Add latest changes from gitlab-org/gitlab@master

2020-01-14 12:07:41 +00:00 · 2020-01-14 12:07:41 +00:00 · 4ce0bee95d
parent 02ab65d49f
commit 4ce0bee95d
93 changed files with 1318 additions and 1134 deletions
--- a/app/assets/javascripts/diffs/components/app.vue
+++ b/app/assets/javascripts/diffs/components/app.vue
@ -6,6 +6,7 @@ import { __ } from '~/locale';
 import createFlash from '~/flash';
 import PanelResizer from '~/vue_shared/components/panel_resizer.vue';
 import glFeatureFlagsMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
+import { isSingleViewStyle } from '~/helpers/diffs_helper';
 import eventHub from '../../notes/event_hub';
 import CompareVersions from './compare_versions.vue';
 import DiffFile from './diff_file.vue';
@ -145,6 +146,9 @@ export default {
  },
  watch: {
    diffViewType() {
+      if (this.needsReload() || this.needsFirstLoad()) {
+        this.refetchDiffData();
+      }
      this.adjustView();
    },
    shouldShow() {
@ -224,6 +228,16 @@ export default {
        { timeout: 1000 },
      );
    },
+    needsReload() {
+      return (
+        this.glFeatures.singleMrDiffView &&
+        this.diffFiles.length &&
+        isSingleViewStyle(this.diffFiles[0])
+      );
+    },
+    needsFirstLoad() {
+      return this.glFeatures.singleMrDiffView && !this.diffFiles.length;
+    },
    fetchData(toggleTree = true) {
      if (this.glFeatures.diffsBatchLoad) {
        this.fetchDiffFilesMeta()
@ -237,6 +251,13 @@ export default {
          });

        this.fetchDiffFilesBatch()
+          .then(() => {
+            // Guarantee the discussions are assigned after the batch finishes.
+            // Just watching the length of the discussions or the diff files
+            // isn't enough, because with split diff loading, neither will
+            // change when loading the other half of the diff files.
+            this.setDiscussions();
+          })
          .then(() => this.startDiffRendering())
          .catch(() => {
            createFlash(__('Something went wrong on our end. Please try again!'));
@ -250,6 +271,7 @@ export default {

            requestIdleCallback(
              () => {
+                this.setDiscussions();
                this.startRenderDiffsQueue();
              },
              { timeout: 1000 },
--- a/app/assets/javascripts/diffs/components/diff_file.vue
+++ b/app/assets/javascripts/diffs/components/diff_file.vue
@ -4,6 +4,7 @@ import _ from 'underscore';
 import { GlLoadingIcon } from '@gitlab/ui';
 import { __, sprintf } from '~/locale';
 import createFlash from '~/flash';
+import { hasDiff } from '~/helpers/diffs_helper';
 import eventHub from '../../notes/event_hub';
 import DiffFileHeader from './diff_file_header.vue';
 import DiffContent from './diff_content.vue';
@ -55,12 +56,7 @@ export default {
      return this.isLoadingCollapsedDiff || (!this.file.renderIt && !this.isCollapsed);
    },
    hasDiff() {
-      return (
-        (this.file.highlighted_diff_lines &&
-          this.file.parallel_diff_lines &&
-          this.file.parallel_diff_lines.length > 0) ||
-        !this.file.blob.readable_text
-      );
+      return hasDiff(this.file);
    },
    isFileTooLarge() {
      return this.file.viewer.error === diffViewerErrors.too_large;
--- a/app/assets/javascripts/diffs/store/actions.js
+++ b/app/assets/javascripts/diffs/store/actions.js
@ -65,6 +65,10 @@ export const fetchDiffFiles = ({ state, commit }) => {
    w: state.showWhitespace ? '0' : '1',
  };

+  if (state.useSingleDiffStyle) {
+    urlParams.view = state.diffViewType;
+  }
+
  commit(types.SET_LOADING, true);

  worker.addEventListener('message', ({ data }) => {
@ -90,13 +94,22 @@ export const fetchDiffFiles = ({ state, commit }) => {
 };

 export const fetchDiffFilesBatch = ({ commit, state }) => {
+  const urlParams = {
+    per_page: DIFFS_PER_PAGE,
+    w: state.showWhitespace ? '0' : '1',
+  };
+
+  if (state.useSingleDiffStyle) {
+    urlParams.view = state.diffViewType;
+  }
+
  commit(types.SET_BATCH_LOADING, true);
  commit(types.SET_RETRIEVING_BATCHES, true);

  const getBatch = page =>
    axios
      .get(state.endpointBatch, {
-        params: { page, per_page: DIFFS_PER_PAGE, w: state.showWhitespace ? '0' : '1' },
+        params: { ...urlParams, page },
      })
      .then(({ data: { pagination, diff_files } }) => {
        commit(types.SET_DIFF_DATA_BATCH, { diff_files });
@ -150,7 +163,10 @@ export const assignDiscussionsToDiff = (
  { commit, state, rootState },
  discussions = rootState.notes.discussions,
 ) => {
-  const diffPositionByLineCode = getDiffPositionByLineCode(state.diffFiles);
+  const diffPositionByLineCode = getDiffPositionByLineCode(
+    state.diffFiles,
+    state.useSingleDiffStyle,
+  );
  const hash = getLocationHash();

  discussions
@ -339,24 +355,23 @@ export const toggleFileDiscussions = ({ getters, dispatch }, diff) => {

 export const toggleFileDiscussionWrappers = ({ commit }, diff) => {
  const discussionWrappersExpanded = allDiscussionWrappersExpanded(diff);
-  let linesWithDiscussions;
-  if (diff.highlighted_diff_lines) {
-    linesWithDiscussions = diff.highlighted_diff_lines.filter(line => line.discussions.length);
-  }
-  if (diff.parallel_diff_lines) {
-    linesWithDiscussions = diff.parallel_diff_lines.filter(
-      line =>
-        (line.left && line.left.discussions.length) ||
-        (line.right && line.right.discussions.length),
-    );
-  }
+  const lineCodesWithDiscussions = new Set();
+  const { parallel_diff_lines: parallelLines, highlighted_diff_lines: inlineLines } = diff;
+  const allLines = inlineLines.concat(
+    parallelLines.map(line => line.left),
+    parallelLines.map(line => line.right),
+  );
+  const lineHasDiscussion = line => Boolean(line?.discussions.length);
+  const registerDiscussionLine = line => lineCodesWithDiscussions.add(line.line_code);

-  if (linesWithDiscussions.length) {
-    linesWithDiscussions.forEach(line => {
+  allLines.filter(lineHasDiscussion).forEach(registerDiscussionLine);
+
+  if (lineCodesWithDiscussions.size) {
+    Array.from(lineCodesWithDiscussions).forEach(lineCode => {
      commit(types.TOGGLE_LINE_DISCUSSIONS, {
        fileHash: diff.file_hash,
-        lineCode: line.line_code,
        expanded: !discussionWrappersExpanded,
+        lineCode,
      });
    });
  }
--- a/app/assets/javascripts/diffs/store/mutations.js
+++ b/app/assets/javascripts/diffs/store/mutations.js
@ -45,26 +45,28 @@ export default {
  },

  [types.SET_DIFF_DATA](state, data) {
+    let files = state.diffFiles;
+
    if (
-      !(
-        gon &&
-        gon.features &&
-        gon.features.diffsBatchLoad &&
-        window.location.search.indexOf('diff_id') === -1
-      )
+      !(gon?.features?.diffsBatchLoad && window.location.search.indexOf('diff_id') === -1) &&
+      data.diff_files
    ) {
-      prepareDiffData(data);
+      files = prepareDiffData(data, files);
    }

    Object.assign(state, {
      ...convertObjectPropsToCamelCase(data),
+      diffFiles: files,
    });
  },

  [types.SET_DIFF_DATA_BATCH](state, data) {
-    prepareDiffData(data);
+    const files = prepareDiffData(data, state.diffFiles);

-    state.diffFiles.push(...data.diff_files);
+    Object.assign(state, {
+      ...convertObjectPropsToCamelCase(data),
+      diffFiles: files,
+    });
  },

  [types.RENDER_FILE](state, file) {
@ -88,11 +90,11 @@ export default {

    if (!diffFile) return;

-    if (diffFile.highlighted_diff_lines) {
+    if (diffFile.highlighted_diff_lines.length) {
      diffFile.highlighted_diff_lines.find(l => l.line_code === lineCode).hasForm = hasForm;
    }

-    if (diffFile.parallel_diff_lines) {
+    if (diffFile.parallel_diff_lines.length) {
      const line = diffFile.parallel_diff_lines.find(l => {
        const { left, right } = l;

@ -153,13 +155,13 @@ export default {
  },

  [types.EXPAND_ALL_FILES](state) {
-    state.diffFiles = state.diffFiles.map(file => ({
-      ...file,
-      viewer: {
-        ...file.viewer,
-        collapsed: false,
-      },
-    }));
+    state.diffFiles.forEach(file => {
+      Object.assign(file, {
+        viewer: Object.assign(file.viewer, {
+          collapsed: false,
+        }),
+      });
+    });
  },

  [types.SET_LINE_DISCUSSIONS_FOR_FILE](state, { discussion, diffPositionByLineCode, hash }) {
@ -197,29 +199,29 @@ export default {
      };
    };

-    state.diffFiles = state.diffFiles.map(diffFile => {
-      if (diffFile.file_hash === fileHash) {
-        const file = { ...diffFile };
-
-        if (file.highlighted_diff_lines) {
-          file.highlighted_diff_lines = file.highlighted_diff_lines.map(line =>
-            setDiscussionsExpanded(lineCheck(line) ? mapDiscussions(line) : line),
-          );
+    state.diffFiles.forEach(file => {
+      if (file.file_hash === fileHash) {
+        if (file.highlighted_diff_lines.length) {
+          file.highlighted_diff_lines.forEach(line => {
+            Object.assign(
+              line,
+              setDiscussionsExpanded(lineCheck(line) ? mapDiscussions(line) : line),
+            );
+          });
        }

-        if (file.parallel_diff_lines) {
-          file.parallel_diff_lines = file.parallel_diff_lines.map(line => {
+        if (file.parallel_diff_lines.length) {
+          file.parallel_diff_lines.forEach(line => {
            const left = line.left && lineCheck(line.left);
            const right = line.right && lineCheck(line.right);

            if (left || right) {
-              return {
-                ...line,
+              Object.assign(line, {
                left: line.left ? setDiscussionsExpanded(mapDiscussions(line.left)) : null,
                right: line.right
                  ? setDiscussionsExpanded(mapDiscussions(line.right, () => !left))
                  : null,
-              };
+              });
            }

            return line;
@ -227,15 +229,15 @@ export default {
        }

        if (!file.parallel_diff_lines || !file.highlighted_diff_lines) {
-          file.discussions = (file.discussions || [])
+          const newDiscussions = (file.discussions || [])
            .filter(d => d.id !== discussion.id)
            .concat(discussion);
+
+          Object.assign(file, {
+            discussions: newDiscussions,
+          });
        }
-
-        return file;
      }
-
-      return diffFile;
    });
  },

@ -259,9 +261,9 @@ export default {
  [types.TOGGLE_LINE_DISCUSSIONS](state, { fileHash, lineCode, expanded }) {
    const selectedFile = state.diffFiles.find(f => f.file_hash === fileHash);

-    updateLineInFile(selectedFile, lineCode, line =>
-      Object.assign(line, { discussionsExpanded: expanded }),
-    );
+    updateLineInFile(selectedFile, lineCode, line => {
+      Object.assign(line, { discussionsExpanded: expanded });
+    });
  },

  [types.TOGGLE_FOLDER_OPEN](state, path) {
--- a/app/assets/javascripts/diffs/store/utils.js
+++ b/app/assets/javascripts/diffs/store/utils.js
@ -185,6 +185,7 @@ export function addContextLines(options) {
 * Trims the first char of the `richText` property when it's either a space or a diff symbol.
 * @param {Object} line
 * @returns {Object}
+ * @deprecated
 */
 export function trimFirstCharOfLineContent(line = {}) {
  // eslint-disable-next-line no-param-reassign
@ -212,79 +213,171 @@ function getLineCode({ left, right }, index) {
  return index;
 }

-// This prepares and optimizes the incoming diff data from the server
-// by setting up incremental rendering and removing unneeded data
-export function prepareDiffData(diffData) {
-  const filesLength = diffData.diff_files.length;
-  let showingLines = 0;
-  for (let i = 0; i < filesLength; i += 1) {
-    const file = diffData.diff_files[i];
-
-    if (file.parallel_diff_lines) {
-      const linesLength = file.parallel_diff_lines.length;
-      for (let u = 0; u < linesLength; u += 1) {
-        const line = file.parallel_diff_lines[u];
-
-        line.line_code = getLineCode(line, u);
-        if (line.left) {
-          line.left = trimFirstCharOfLineContent(line.left);
-          line.left.discussions = [];
-          line.left.hasForm = false;
-        }
-        if (line.right) {
-          line.right = trimFirstCharOfLineContent(line.right);
-          line.right.discussions = [];
-          line.right.hasForm = false;
-        }
-      }
-    }
-
-    if (file.highlighted_diff_lines) {
-      const linesLength = file.highlighted_diff_lines.length;
-      for (let u = 0; u < linesLength; u += 1) {
-        const line = file.highlighted_diff_lines[u];
-        Object.assign(line, {
-          ...trimFirstCharOfLineContent(line),
-          discussions: [],
-          hasForm: false,
-        });
-      }
-      showingLines += file.parallel_diff_lines.length;
-    }
-
-    const name = (file.viewer && file.viewer.name) || diffViewerModes.text;
-
-    Object.assign(file, {
-      renderIt: showingLines < LINES_TO_BE_RENDERED_DIRECTLY,
-      collapsed: name === diffViewerModes.text && showingLines > MAX_LINES_TO_BE_RENDERED,
-      isShowingFullFile: false,
-      isLoadingFullFile: false,
-      discussions: [],
-      renderingLines: false,
-    });
-  }
+function diffFileUniqueId(file) {
+  return `${file.content_sha}-${file.file_hash}`;
 }

-export function getDiffPositionByLineCode(diffFiles) {
-  return diffFiles.reduce((acc, diffFile) => {
-    // We can only use highlightedDiffLines to create the map of diff lines because
-    // highlightedDiffLines will also include every parallel diff line in it.
-    if (diffFile.highlighted_diff_lines) {
+function combineDiffFilesWithPriorFiles(files, prior = []) {
+  files.forEach(file => {
+    const id = diffFileUniqueId(file);
+    const oldMatch = prior.find(oldFile => diffFileUniqueId(oldFile) === id);
+
+    if (oldMatch) {
+      const missingInline = !file.highlighted_diff_lines;
+      const missingParallel = !file.parallel_diff_lines;
+
+      if (missingInline) {
+        Object.assign(file, {
+          highlighted_diff_lines: oldMatch.highlighted_diff_lines,
+        });
+      }
+
+      if (missingParallel) {
+        Object.assign(file, {
+          parallel_diff_lines: oldMatch.parallel_diff_lines,
+        });
+      }
+    }
+  });
+
+  return files;
+}
+
+function ensureBasicDiffFileLines(file) {
+  const missingInline = !file.highlighted_diff_lines;
+  const missingParallel = !file.parallel_diff_lines;
+
+  Object.assign(file, {
+    highlighted_diff_lines: missingInline ? [] : file.highlighted_diff_lines,
+    parallel_diff_lines: missingParallel ? [] : file.parallel_diff_lines,
+  });
+
+  return file;
+}
+
+function cleanRichText(text) {
+  return text ? text.replace(/^[+ -]/, '') : undefined;
+}
+
+function prepareLine(line) {
+  return Object.assign(line, {
+    rich_text: cleanRichText(line.rich_text),
+    discussionsExpanded: true,
+    discussions: [],
+    hasForm: false,
+    text: undefined,
+  });
+}
+
+function prepareDiffFileLines(file) {
+  const inlineLines = file.highlighted_diff_lines;
+  const parallelLines = file.parallel_diff_lines;
+  let parallelLinesCount = 0;
+
+  inlineLines.forEach(prepareLine);
+
+  parallelLines.forEach((line, index) => {
+    Object.assign(line, { line_code: getLineCode(line, index) });
+
+    if (line.left) {
+      parallelLinesCount += 1;
+      prepareLine(line.left);
+    }
+
+    if (line.right) {
+      parallelLinesCount += 1;
+      prepareLine(line.right);
+    }
+
+    Object.assign(file, {
+      inlineLinesCount: inlineLines.length,
+      parallelLinesCount,
+    });
+  });
+
+  return file;
+}
+
+function getVisibleDiffLines(file) {
+  return Math.max(file.inlineLinesCount, file.parallelLinesCount);
+}
+
+function finalizeDiffFile(file) {
+  const name = (file.viewer && file.viewer.name) || diffViewerModes.text;
+  const lines = getVisibleDiffLines(file);
+
+  Object.assign(file, {
+    renderIt: lines < LINES_TO_BE_RENDERED_DIRECTLY,
+    collapsed: name === diffViewerModes.text && lines > MAX_LINES_TO_BE_RENDERED,
+    isShowingFullFile: false,
+    isLoadingFullFile: false,
+    discussions: [],
+    renderingLines: false,
+  });
+
+  return file;
+}
+
+export function prepareDiffData(diffData, priorFiles) {
+  return combineDiffFilesWithPriorFiles(diffData.diff_files, priorFiles)
+    .map(ensureBasicDiffFileLines)
+    .map(prepareDiffFileLines)
+    .map(finalizeDiffFile);
+}
+
+export function getDiffPositionByLineCode(diffFiles, useSingleDiffStyle) {
+  let lines = [];
+  const hasInlineDiffs = diffFiles.some(file => file.highlighted_diff_lines.length > 0);
+
+  if (!useSingleDiffStyle || hasInlineDiffs) {
+    // In either of these cases, we can use `highlighted_diff_lines` because
+    // that will include all of the parallel diff lines, too
+
+    lines = diffFiles.reduce((acc, diffFile) => {
      diffFile.highlighted_diff_lines.forEach(line => {
-        if (line.line_code) {
-          acc[line.line_code] = {
-            base_sha: diffFile.diff_refs.base_sha,
-            head_sha: diffFile.diff_refs.head_sha,
-            start_sha: diffFile.diff_refs.start_sha,
-            new_path: diffFile.new_path,
-            old_path: diffFile.old_path,
-            old_line: line.old_line,
-            new_line: line.new_line,
-            line_code: line.line_code,
-            position_type: 'text',
-          };
+        acc.push({ file: diffFile, line });
+      });
+
+      return acc;
+    }, []);
+  } else {
+    // If we're in single diff view mode and the inline lines haven't been
+    // loaded yet, we need to parse the parallel lines
+
+    lines = diffFiles.reduce((acc, diffFile) => {
+      diffFile.parallel_diff_lines.forEach(pair => {
+        // It's possible for a parallel line to have an opposite line that doesn't exist
+        // For example: *deleted* lines will have `null` right lines, while
+        // *added* lines will have `null` left lines.
+        // So we have to check each line before we push it onto the array so we're not
+        // pushing null line diffs
+
+        if (pair.left) {
+          acc.push({ file: diffFile, line: pair.left });
+        }
+
+        if (pair.right) {
+          acc.push({ file: diffFile, line: pair.right });
        }
      });
+
+      return acc;
+    }, []);
+  }
+
+  return lines.reduce((acc, { file, line }) => {
+    if (line.line_code) {
+      acc[line.line_code] = {
+        base_sha: file.diff_refs.base_sha,
+        head_sha: file.diff_refs.head_sha,
+        start_sha: file.diff_refs.start_sha,
+        new_path: file.new_path,
+        old_path: file.old_path,
+        old_line: line.old_line,
+        new_line: line.new_line,
+        line_code: line.line_code,
+        position_type: 'text',
+      };
    }

    return acc;
@ -462,47 +555,47 @@ export const convertExpandLines = ({

 export const idleCallback = cb => requestIdleCallback(cb);

+function getLinesFromFileByLineCode(file, lineCode) {
+  const parallelLines = file.parallel_diff_lines;
+  const inlineLines = file.highlighted_diff_lines;
+  const matchesCode = line => line.line_code === lineCode;
+
+  return [
+    ...parallelLines.reduce((acc, line) => {
+      if (line.left) {
+        acc.push(line.left);
+      }
+
+      if (line.right) {
+        acc.push(line.right);
+      }
+
+      return acc;
+    }, []),
+    ...inlineLines,
+  ].filter(matchesCode);
+}
+
 export const updateLineInFile = (selectedFile, lineCode, updateFn) => {
-  if (selectedFile.parallel_diff_lines) {
-    const targetLine = selectedFile.parallel_diff_lines.find(
-      line =>
-        (line.left && line.left.line_code === lineCode) ||
-        (line.right && line.right.line_code === lineCode),
-    );
-    if (targetLine) {
-      const side = targetLine.left && targetLine.left.line_code === lineCode ? 'left' : 'right';
-
-      updateFn(targetLine[side]);
-    }
-  }
-  if (selectedFile.highlighted_diff_lines) {
-    const targetInlineLine = selectedFile.highlighted_diff_lines.find(
-      line => line.line_code === lineCode,
-    );
-
-    if (targetInlineLine) {
-      updateFn(targetInlineLine);
-    }
-  }
+  getLinesFromFileByLineCode(selectedFile, lineCode).forEach(updateFn);
 };

 export const allDiscussionWrappersExpanded = diff => {
-  const discussionsExpandedArray = [];
-  if (diff.parallel_diff_lines) {
-    diff.parallel_diff_lines.forEach(line => {
-      if (line.left && line.left.discussions.length) {
-        discussionsExpandedArray.push(line.left.discussionsExpanded);
-      }
-      if (line.right && line.right.discussions.length) {
-        discussionsExpandedArray.push(line.right.discussionsExpanded);
-      }
-    });
-  } else if (diff.highlighted_diff_lines) {
-    diff.highlighted_diff_lines.forEach(line => {
-      if (line.discussions.length) {
-        discussionsExpandedArray.push(line.discussionsExpanded);
-      }
-    });
-  }
-  return discussionsExpandedArray.every(el => el);
+  let discussionsExpanded = true;
+  const changeExpandedResult = line => {
+    if (line && line.discussions.length) {
+      discussionsExpanded = discussionsExpanded && line.discussionsExpanded;
+    }
+  };
+
+  diff.parallel_diff_lines.forEach(line => {
+    changeExpandedResult(line.left);
+    changeExpandedResult(line.right);
+  });
+
+  diff.highlighted_diff_lines.forEach(line => {
+    changeExpandedResult(line);
+  });
+
+  return discussionsExpanded;
 };
--- a/app/assets/javascripts/error_tracking/components/error_details.vue
+++ b/app/assets/javascripts/error_tracking/components/error_details.vue
@ -1,6 +1,7 @@
 <script>
 import { mapActions, mapGetters, mapState } from 'vuex';
 import dateFormat from 'dateformat';
+import createFlash from '~/flash';
 import { GlFormInput, GlLink, GlLoadingIcon, GlBadge } from '@gitlab/ui';
 import { __, sprintf, n__ } from '~/locale';
 import LoadingButton from '~/vue_shared/components/loading_button.vue';
@ -11,6 +12,8 @@ import TrackEventDirective from '~/vue_shared/directives/track_event';
 import timeagoMixin from '~/vue_shared/mixins/timeago';
 import { trackClickErrorLinkToSentryOptions } from '../utils';

+import query from '../queries/details.query.graphql';
+
 export default {
  components: {
    LoadingButton,
@ -27,6 +30,14 @@ export default {
  },
  mixins: [timeagoMixin],
  props: {
+    issueId: {
+      type: String,
+      required: true,
+    },
+    projectPath: {
+      type: String,
+      required: true,
+    },
    issueDetailsPath: {
      type: String,
      required: true,
@ -44,8 +55,28 @@ export default {
      required: true,
    },
  },
+  apollo: {
+    GQLerror: {
+      query,
+      variables() {
+        return {
+          fullPath: this.projectPath,
+          errorId: `gid://gitlab/Gitlab::ErrorTracking::DetailedError/${this.issueId}`,
+        };
+      },
+      pollInterval: 2000,
+      update: data => data.project.sentryDetailedError,
+      error: () => createFlash(__('Failed to load error details from Sentry.')),
+      result(res) {
+        if (res.data.project?.sentryDetailedError) {
+          this.$apollo.queries.GQLerror.stopPolling();
+        }
+      },
+    },
+  },
  data() {
    return {
+      GQLerror: null,
      issueCreationInProgress: false,
    };
  },
@ -56,26 +87,28 @@ export default {
      return sprintf(
        __('Reported %{timeAgo} by %{reportedBy}'),
        {
-          reportedBy: `<strong>${this.error.culprit}</strong>`,
+          reportedBy: `<strong>${this.GQLerror.culprit}</strong>`,
          timeAgo: this.timeFormatted(this.stacktraceData.date_received),
        },
        false,
      );
    },
    firstReleaseLink() {
-      return `${this.error.external_base_url}/releases/${this.error.first_release_short_version}`;
+      return `${this.error.external_base_url}/releases/${this.GQLerror.firstReleaseShortVersion}`;
    },
    lastReleaseLink() {
-      return `${this.error.external_base_url}releases/${this.error.last_release_short_version}`;
+      return `${this.error.external_base_url}releases/${this.GQLerror.lastReleaseShortVersion}`;
    },
    showDetails() {
-      return Boolean(!this.loading && this.error && this.error.id);
+      return Boolean(
+        !this.loading && !this.$apollo.queries.GQLerror.loading && this.error && this.GQLerror,
+      );
    },
    showStacktrace() {
      return Boolean(!this.loadingStacktrace && this.stacktrace && this.stacktrace.length);
    },
    issueTitle() {
-      return this.error.title;
+      return this.GQLerror.title;
    },
    issueDescription() {
      return sprintf(
@ -84,13 +117,13 @@ export default {
        ),
        {
          description: '# Error Details:\n',
-          errorUrl: `${this.error.external_url}\n`,
-          firstSeen: `\n${this.error.first_seen}\n`,
-          lastSeen: `${this.error.last_seen}\n`,
-          countLabel: n__('- Event', '- Events', this.error.count),
-          count: `${this.error.count}\n`,
-          userCountLabel: n__('- User', '- Users', this.error.user_count),
-          userCount: `${this.error.user_count}\n`,
+          errorUrl: `${this.GQLerror.externalUrl}\n`,
+          firstSeen: `\n${this.GQLerror.firstSeen}\n`,
+          lastSeen: `${this.GQLerror.lastSeen}\n`,
+          countLabel: n__('- Event', '- Events', this.GQLerror.count),
+          count: `${this.GQLerror.count}\n`,
+          userCountLabel: n__('- User', '- Users', this.GQLerror.userCount),
+          userCount: `${this.GQLerror.userCount}\n`,
        },
        false,
      );
@ -119,7 +152,7 @@ export default {

 <template>
  <div>
-    <div v-if="loading" class="py-3">
+    <div v-if="$apollo.queries.GQLerror.loading || loading" class="py-3">
      <gl-loading-icon :size="3" />
    </div>
    <div v-else-if="showDetails" class="error-details">
@ -129,7 +162,7 @@ export default {
          <gl-form-input class="hidden" name="issue[title]" :value="issueTitle" />
          <input name="issue[description]" :value="issueDescription" type="hidden" />
          <gl-form-input
-            :value="error.id"
+            :value="GQLerror.id"
            class="hidden"
            name="issue[sentry_issue_attributes][sentry_issue_identifier]"
          />
@ -145,16 +178,16 @@ export default {
        </form>
      </div>
      <div>
-        <tooltip-on-truncate :title="error.title" truncate-target="child" placement="top">
-          <h2 class="text-truncate">{{ error.title }}</h2>
+        <tooltip-on-truncate :title="GQLerror.title" truncate-target="child" placement="top">
+          <h2 class="text-truncate">{{ GQLerror.title }}</h2>
        </tooltip-on-truncate>
        <template v-if="error.tags">
-          <gl-badge v-if="error.tags.level" variant="danger" class="rounded-pill mr-2">{{
-            errorLevel
-          }}</gl-badge>
-          <gl-badge v-if="error.tags.logger" variant="light" class="rounded-pill">{{
-            error.tags.logger
-          }}</gl-badge>
+          <gl-badge v-if="error.tags.level" variant="danger" class="rounded-pill mr-2"
+            >{{ errorLevel }}
+          </gl-badge>
+          <gl-badge v-if="error.tags.logger" variant="light" class="rounded-pill"
+            >{{ error.tags.logger }}
+          </gl-badge>
        </template>

        <h3>{{ __('Error details') }}</h3>
@ -168,35 +201,35 @@ export default {
          <li>
            <span class="bold">{{ __('Sentry event') }}:</span>
            <gl-link
-              v-track-event="trackClickErrorLinkToSentryOptions(error.external_url)"
-              :href="error.external_url"
+              v-track-event="trackClickErrorLinkToSentryOptions(GQLerror.externalUrl)"
+              :href="GQLerror.externalUrl"
              target="_blank"
            >
-              <span class="text-truncate">{{ error.external_url }}</span>
+              <span class="text-truncate">{{ GQLerror.externalUrl }}</span>
              <icon name="external-link" class="ml-1 flex-shrink-0" />
            </gl-link>
          </li>
-          <li v-if="error.first_release_short_version">
+          <li v-if="GQLerror.firstReleaseShortVersion">
            <span class="bold">{{ __('First seen') }}:</span>
-            {{ formatDate(error.first_seen) }}
+            {{ formatDate(GQLerror.firstSeen) }}
            <gl-link :href="firstReleaseLink" target="_blank">
-              <span>{{ __('Release') }}: {{ error.first_release_short_version }}</span>
+              <span>{{ __('Release') }}: {{ GQLerror.firstReleaseShortVersion }}</span>
            </gl-link>
          </li>
-          <li v-if="error.last_release_short_version">
+          <li v-if="GQLerror.lastReleaseShortVersion">
            <span class="bold">{{ __('Last seen') }}:</span>
-            {{ formatDate(error.last_seen) }}
+            {{ formatDate(GQLerror.lastSeen) }}
            <gl-link :href="lastReleaseLink" target="_blank">
-              <span>{{ __('Release') }}: {{ error.last_release_short_version }}</span>
+              <span>{{ __('Release') }}: {{ GQLerror.lastReleaseShortVersion }}</span>
            </gl-link>
          </li>
          <li>
            <span class="bold">{{ __('Events') }}:</span>
-            <span>{{ error.count }}</span>
+            <span>{{ GQLerror.count }}</span>
          </li>
          <li>
            <span class="bold">{{ __('Users') }}:</span>
-            <span>{{ error.user_count }}</span>
+            <span>{{ GQLerror.userCount }}</span>
          </li>
        </ul>

--- a/app/assets/javascripts/error_tracking/details.js
+++ b/app/assets/javascripts/error_tracking/details.js
@ -1,22 +1,39 @@
 import Vue from 'vue';
+import VueApollo from 'vue-apollo';
+import createDefaultClient from '~/lib/graphql';
 import store from './store';
 import ErrorDetails from './components/error_details.vue';
 import csrf from '~/lib/utils/csrf';

+Vue.use(VueApollo);
+
 export default () => {
+  const apolloProvider = new VueApollo({
+    defaultClient: createDefaultClient(),
+  });
+
  // eslint-disable-next-line no-new
  new Vue({
    el: '#js-error_details',
+    apolloProvider,
    components: {
      ErrorDetails,
    },
    store,
    render(createElement) {
      const domEl = document.querySelector(this.$options.el);
-      const { issueDetailsPath, issueStackTracePath, projectIssuesPath } = domEl.dataset;
+      const {
+        issueId,
+        projectPath,
+        issueDetailsPath,
+        issueStackTracePath,
+        projectIssuesPath,
+      } = domEl.dataset;

      return createElement('error-details', {
        props: {
+          issueId,
+          projectPath,
          issueDetailsPath,
          issueStackTracePath,
          projectIssuesPath,
--- a/app/assets/javascripts/error_tracking/queries/details.query.graphql
+++ b/app/assets/javascripts/error_tracking/queries/details.query.graphql
@ -0,0 +1,18 @@
+query errorDetails($fullPath: ID!, $errorId: ID!) {
+    project(fullPath: $fullPath) {
+        sentryDetailedError(id: $errorId) {
+            id
+            sentryId
+            title
+            userCount
+            count
+            firstSeen
+            lastSeen
+            message
+            culprit
+            externalUrl
+            firstReleaseShortVersion
+            lastReleaseShortVersion
+        }
+    }
+}
--- a/app/assets/javascripts/helpers/diffs_helper.js
+++ b/app/assets/javascripts/helpers/diffs_helper.js
@ -0,0 +1,19 @@
+export function hasInlineLines(diffFile) {
+  return diffFile?.highlighted_diff_lines?.length > 0; /* eslint-disable-line camelcase */
+}
+
+export function hasParallelLines(diffFile) {
+  return diffFile?.parallel_diff_lines?.length > 0; /* eslint-disable-line camelcase */
+}
+
+export function isSingleViewStyle(diffFile) {
+  return !hasParallelLines(diffFile) || !hasInlineLines(diffFile);
+}
+
+export function hasDiff(diffFile) {
+  return (
+    hasInlineLines(diffFile) ||
+    hasParallelLines(diffFile) ||
+    !diffFile?.blob?.readable_text /* eslint-disable-line camelcase */
+  );
+}
--- a/app/assets/javascripts/monitoring/stores/actions.js
+++ b/app/assets/javascripts/monitoring/stores/actions.js
@ -39,7 +39,7 @@ export const requestMetricsDashboard = ({ commit }) => {
 };
 export const receiveMetricsDashboardSuccess = ({ commit, dispatch }, { response, params }) => {
  commit(types.SET_ALL_DASHBOARDS, response.all_dashboards);
-  commit(types.RECEIVE_METRICS_DATA_SUCCESS, response.dashboard.panel_groups);
+  commit(types.RECEIVE_METRICS_DATA_SUCCESS, response.dashboard);
  return dispatch('fetchPrometheusMetrics', params);
 };
 export const receiveMetricsDashboardFailure = ({ commit }, error) => {
--- a/app/assets/javascripts/monitoring/stores/mutations.js
+++ b/app/assets/javascripts/monitoring/stores/mutations.js
@ -84,23 +84,26 @@ export default {
    state.emptyState = 'loading';
    state.showEmptyState = true;
  },
-  [types.RECEIVE_METRICS_DATA_SUCCESS](state, groupData) {
-    state.dashboard.panel_groups = groupData.map((group, i) => {
-      const key = `${slugify(group.group || 'default')}-${i}`;
-      let { panels = [] } = group;
+  [types.RECEIVE_METRICS_DATA_SUCCESS](state, dashboard) {
+    state.dashboard = {
+      ...dashboard,
+      panel_groups: dashboard.panel_groups.map((group, i) => {
+        const key = `${slugify(group.group || 'default')}-${i}`;
+        let { panels = [] } = group;

-      // each panel has metric information that needs to be normalized
-      panels = panels.map(panel => ({
-        ...panel,
-        metrics: normalizePanelMetrics(panel.metrics, panel.y_label),
-      }));
+        // each panel has metric information that needs to be normalized
+        panels = panels.map(panel => ({
+          ...panel,
+          metrics: normalizePanelMetrics(panel.metrics, panel.y_label),
+        }));

-      return {
-        ...group,
-        panels,
-        key,
-      };
-    });
+        return {
+          ...group,
+          panels,
+          key,
+        };
+      }),
+    };

    if (!state.dashboard.panel_groups.length) {
      state.emptyState = 'noData';
--- a/app/helpers/projects/error_tracking_helper.rb
+++ b/app/helpers/projects/error_tracking_helper.rb
@ -18,9 +18,11 @@ module Projects::ErrorTrackingHelper
    opts = [project, issue_id, { format: :json }]

    {
-      'project-issues-path' => project_issues_path(project),
+      'issue-id' => issue_id,
+      'project-path' => project.full_path,
      'issue-details-path' => details_project_error_tracking_index_path(*opts),
      'issue-update-path' => update_project_error_tracking_index_path(*opts),
+      'project-issues-path' => project_issues_path(project),
      'issue-stack-trace-path' => stack_trace_project_error_tracking_index_path(*opts)
    }
  end
--- a/app/models/ci/trigger.rb
+++ b/app/models/ci/trigger.rb
@ -11,7 +11,7 @@ module Ci
    has_many :trigger_requests

    validates :token, presence: true, uniqueness: true
-    validates :owner, presence: true, unless: :supports_legacy_tokens?
+    validates :owner, presence: true

    before_validation :set_default_values

@ -31,17 +31,8 @@ module Ci
      token[0...4] if token.present?
    end

-    def legacy?
-      self.owner_id.blank?
-    end
-
-    def supports_legacy_tokens?
-      Feature.enabled?(:use_legacy_pipeline_triggers, project)
-    end
-
    def can_access_project?
-      supports_legacy_tokens? && legacy? ||
-        Ability.allowed?(self.owner, :create_build, project)
+      Ability.allowed?(self.owner, :create_build, project)
    end
  end
 end
--- a/app/policies/ci/trigger_policy.rb
+++ b/app/policies/ci/trigger_policy.rb
@ -5,13 +5,12 @@ module Ci
    delegate { @subject.project }

    with_options scope: :subject, score: 0
-    condition(:legacy) { @subject.supports_legacy_tokens? && @subject.legacy? }

    with_score 0
    condition(:is_owner) { @user && @subject.owner_id == @user.id }

    rule { ~can?(:admin_build) }.prevent :admin_trigger
-    rule { legacy | is_owner }.enable :admin_trigger
+    rule { is_owner }.enable :admin_trigger

    rule { can?(:admin_build) }.enable :manage_trigger
  end
--- a/app/views/errors/_footer.html.haml
+++ b/app/views/errors/_footer.html.haml
@ -4,7 +4,7 @@
      = link_to s_('Nav|Home'), root_path
    %li
      - if current_user
-        = link_to s_('Nav|Sign out and sign in with a different account'), destroy_user_session_path
+        = link_to s_('Nav|Sign out and sign in with a different account'), destroy_user_session_path, method: :post
      - else
        = link_to s_('Nav|Sign In / Register'), new_session_path(:user, redirect_to_referer: 'yes')
    %li
--- a/app/views/layouts/header/_current_user_dropdown.html.haml
+++ b/app/views/layouts/header/_current_user_dropdown.html.haml
@ -47,4 +47,4 @@
  - if current_user_menu?(:sign_out)
    %li.divider
    %li
-      = link_to _("Sign out"), destroy_user_session_path, class: "sign-out-link", data: { qa_selector: 'sign_out_link' }
+      = link_to _("Sign out"), destroy_user_session_path, method: :post, class: "sign-out-link", data: { qa_selector: 'sign_out_link' }
--- a/app/views/layouts/nav/_dashboard.html.haml
+++ b/app/views/layouts/nav/_dashboard.html.haml
@ -55,7 +55,7 @@
          - if Feature.enabled?(:user_mode_in_session)
            - if header_link?(:admin_mode)
              = nav_link(controller: 'admin/sessions') do
-                = link_to destroy_admin_session_path, class: 'd-lg-none lock-open-icon' do
+                = link_to destroy_admin_session_path, method: :post, class: 'd-lg-none lock-open-icon' do
                  = _('Leave Admin Mode')
            - elsif current_user.admin?
              = nav_link(controller: 'admin/sessions') do
--- a/app/views/projects/triggers/_content.html.haml
+++ b/app/views/projects/triggers/_content.html.haml
@ -1,9 +0,0 @@
- if Feature.enabled?(:use_legacy_pipeline_triggers, @project)
-  %p.append-bottom-default
-    Triggers with the
-    %span.badge.badge-primary legacy
-    label do not have an associated user and only have access to the current project.
-    %br
-    = succeed '.' do
-      Learn more in the
-      = link_to 'triggers documentation', help_page_path('ci/triggers/README'), target: '_blank'
--- a/app/views/projects/triggers/_index.html.haml
+++ b/app/views/projects/triggers/_index.html.haml
@ -1,6 +1,5 @@
 .row.prepend-top-default.append-bottom-default.triggers-container
  .col-lg-12
-    = render "projects/triggers/content"
    .card
      .card-header
        Manage your project's triggers
--- a/app/views/projects/triggers/_trigger.html.haml
+++ b/app/views/projects/triggers/_trigger.html.haml
@ -7,12 +7,7 @@
      %span= trigger.short_token

    .label-container
-      - if trigger.legacy?
-        - if trigger.supports_legacy_tokens?
-          %span.badge.badge-primary.has-tooltip{ title: "Trigger makes use of deprecated functionality" } legacy
-        - else
-          %span.badge.badge-danger.has-tooltip{ title: "Trigger is invalid due to being a legacy trigger. We recommend replacing it with a new trigger" } invalid
-      - elsif !trigger.can_access_project?
+      - unless trigger.can_access_project?
        %span.badge.badge-danger.has-tooltip{ title: "Trigger user has insufficient permissions to project" } invalid

  %td
--- a/app/views/projects/triggers/edit.html.haml
+++ b/app/views/projects/triggers/edit.html.haml
@ -1,9 +1,7 @@
 - page_title "Trigger"

 .row.prepend-top-default.append-bottom-default
-  .col-lg-3
-    = render "content"
-  .col-lg-9
+  .col-lg-12
    %h4.prepend-top-0
      Update trigger
    = render "form", btn_text: "Save trigger"
--- a/changelogs/unreleased/14857-activate-promethus-integration-for-projects.yml
+++ b/changelogs/unreleased/14857-activate-promethus-integration-for-projects.yml
@ -1,5 +0,0 @@
---
-title: Migrate the database to activate projects prometheus service integration for projects with prometheus installed on shared k8s cluster.
-merge_request: 19956
-author:
-type: fixed
--- a/changelogs/unreleased/29772-completely-removing-use_legacy_pipeline_triggers.yml
+++ b/changelogs/unreleased/29772-completely-removing-use_legacy_pipeline_triggers.yml
@ -0,0 +1,5 @@
+---
+title: Remove feature flag 'use_legacy_pipeline_triggers' and remove legacy tokens
+merge_request: 21732
+author:
+type: removed
--- a/changelogs/unreleased/34867-epics_to_project_import_export.yml
+++ b/changelogs/unreleased/34867-epics_to_project_import_export.yml
@ -0,0 +1,5 @@
+---
+title: Add epics to project import/export
+merge_request: 19883
+author:
+type: added
--- a/changelogs/unreleased/39979-grapql-for-error-details.yml
+++ b/changelogs/unreleased/39979-grapql-for-error-details.yml
@ -0,0 +1,5 @@
+---
+title: Use GraphQL to load error tracking detail page content
+merge_request: 22422
+author:
+type: performance
--- a/changelogs/unreleased/enable-parent-child-pipelines.yml
+++ b/changelogs/unreleased/enable-parent-child-pipelines.yml
@ -0,0 +1,5 @@
+---
+title: Allow a pipeline (parent) to create a child pipeline as downstream pipeline within the same project
+merge_request: 21830
+author:
+type: added
--- a/changelogs/unreleased/feature-split-diff-attempt-3.yml
+++ b/changelogs/unreleased/feature-split-diff-attempt-3.yml
@ -0,0 +1,5 @@
+---
+title: Load MR diff types lazily to reduce initial diff payload size
+merge_request: 19930
+author:
+type: added
--- a/changelogs/unreleased/refactor-session-disable-with-post.yml
+++ b/changelogs/unreleased/refactor-session-disable-with-post.yml
@ -0,0 +1,5 @@
+---
+title: User signout and admin mode disable use now POST instead of GET
+merge_request: 22113
+author: Diego Louzán
+type: other
--- a/config/initializers/8_devise.rb
+++ b/config/initializers/8_devise.rb
@ -203,7 +203,7 @@ Devise.setup do |config|
  config.navigational_formats = [:"*/*", "*/*", :html, :zip]

  # The default HTTP method used to sign out a resource. Default is :delete.
-  config.sign_out_via = :get
+  config.sign_out_via = :post

  # ==> OmniAuth
  # To configure a new OmniAuth provider copy and edit omniauth.rb.sample
--- a/config/routes/admin.rb
+++ b/config/routes/admin.rb
@ -24,7 +24,7 @@ namespace :admin do
  end

  resource :session, only: [:new, :create] do
-    get 'destroy', action: :destroy, as: :destroy
+    post 'destroy', action: :destroy, as: :destroy
  end

  resource :impersonation, only: :destroy
--- a/db/post_migrate/20191204114127_delete_legacy_triggers.rb
+++ b/db/post_migrate/20191204114127_delete_legacy_triggers.rb
@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class DeleteLegacyTriggers < ActiveRecord::Migration[5.2]
+  DOWNTIME = false
+
+  def up
+    execute <<~SQL
+      DELETE FROM ci_triggers WHERE owner_id IS NULL
+    SQL
+
+    change_column_null :ci_triggers, :owner_id, false
+  end
+
+  def down
+    change_column_null :ci_triggers, :owner_id, true
+  end
+end
--- a/db/post_migrate/20191220102807_patch_prometheus_services_for_shared_cluster_applications.rb
+++ b/db/post_migrate/20191220102807_patch_prometheus_services_for_shared_cluster_applications.rb
@ -1,88 +0,0 @@
-# frozen_string_literal: true
-
-class PatchPrometheusServicesForSharedClusterApplications < ActiveRecord::Migration[5.2]
-  include Gitlab::Database::MigrationHelpers
-
-  DOWNTIME = false
-  MIGRATION = 'ActivatePrometheusServicesForSharedClusterApplications'.freeze
-  BATCH_SIZE = 500
-  DELAY = 2.minutes
-
-  disable_ddl_transaction!
-
-  module Migratable
-    module Applications
-      class Prometheus < ActiveRecord::Base
-        self.table_name = 'clusters_applications_prometheus'
-
-        enum status: {
-          errored: -1,
-          installed: 3,
-          updated: 5
-        }
-      end
-    end
-
-    class Project < ActiveRecord::Base
-      self.table_name = 'projects'
-      include ::EachBatch
-
-      scope :with_application_on_group_clusters, -> {
-        joins("INNER JOIN namespaces ON namespaces.id = projects.namespace_id")
-          .joins("INNER JOIN cluster_groups ON cluster_groups.group_id = namespaces.id")
-          .joins("INNER JOIN clusters ON clusters.id = cluster_groups.cluster_id AND clusters.cluster_type = #{Cluster.cluster_types['group_type']}")
-          .joins("INNER JOIN clusters_applications_prometheus ON clusters_applications_prometheus.cluster_id = clusters.id
-                      AND clusters_applications_prometheus.status IN (#{Applications::Prometheus.statuses[:installed]}, #{Applications::Prometheus.statuses[:updated]})")
-      }
-
-      scope :without_active_prometheus_services, -> {
-        joins("LEFT JOIN services ON services.project_id = projects.id AND services.type = 'PrometheusService'")
-          .where("services.id IS NULL OR (services.active = FALSE AND services.properties = '{}')")
-      }
-    end
-
-    class Cluster < ActiveRecord::Base
-      self.table_name = 'clusters'
-
-      enum cluster_type: {
-        instance_type: 1,
-        group_type: 2
-      }
-
-      def self.has_prometheus_application?
-        joins("INNER JOIN clusters_applications_prometheus ON clusters_applications_prometheus.cluster_id = clusters.id
-                   AND clusters_applications_prometheus.status IN (#{Applications::Prometheus.statuses[:installed]}, #{Applications::Prometheus.statuses[:updated]})").exists?
-      end
-    end
-  end
-
-  def up
-    projects_without_active_prometheus_service.group('projects.id').each_batch(of: BATCH_SIZE) do |batch, index|
-      bg_migrations_batch = batch.select('projects.id').map { |project| [MIGRATION, project.id] }
-      delay = index * DELAY
-      BackgroundMigrationWorker.bulk_perform_in(delay.seconds, bg_migrations_batch)
-    end
-  end
-
-  def down
-    # no-op
-  end
-
-  private
-
-  def projects_without_active_prometheus_service
-    scope = Migratable::Project.without_active_prometheus_services
-
-    return scope if migrate_instance_cluster?
-
-    scope.with_application_on_group_clusters
-  end
-
-  def migrate_instance_cluster?
-    if instance_variable_defined?('@migrate_instance_cluster')
-      @migrate_instance_cluster
-    else
-      @migrate_instance_cluster = Migratable::Cluster.instance_type.has_prometheus_application?
-    end
-  end
-end
--- a/db/schema.rb
+++ b/db/schema.rb
@ -994,7 +994,7 @@ ActiveRecord::Schema.define(version: 2020_01_08_233040) do
    t.datetime "created_at"
    t.datetime "updated_at"
    t.integer "project_id"
-    t.integer "owner_id"
+    t.integer "owner_id", null: false
    t.string "description"
    t.string "ref"
    t.index ["owner_id"], name: "index_ci_triggers_on_owner_id"
--- a/doc/ci/img/parent_pipeline_graph_expanded_v12_6.png
+++ b/doc/ci/img/parent_pipeline_graph_expanded_v12_6.png
--- a/doc/ci/parent_child_pipelines.md
+++ b/doc/ci/parent_child_pipelines.md
@ -0,0 +1,86 @@
+---
+type: reference
+---
+
+# Parent-child pipelines
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/16094) in GitLab Starter 12.7.
+
+As pipelines grow more complex, a few related problems start to emerge:
+
+- The staged structure, where all steps in a stage must be completed before the first
+  job in next stage begins, causes arbitrary waits, slowing things down.
+- Configuration for the single global pipeline becomes very long and complicated,
+  making it hard to manage.
+- Imports with [`include`](yaml/README.md#include) increase the complexity of the configuration, and create the potential
+  for namespace collisions where jobs are unintentionally duplicated.
+- Pipeline UX can become unwieldy with so many jobs and stages to work with.
+
+Additionally, sometimes the behavior of a pipeline needs to be more dynamic. The ability
+to choose to start sub-pipelines (or not) is a powerful ability, especially if the
+YAML is dynamically generated.
+
+![Parent pipeline graph expanded](img/parent_pipeline_graph_expanded_v12_6.png)
+
+Similarly to [multi-project pipelines](multi_project_pipelines.md), a pipeline can trigger a
+set of concurrently running child pipelines, but within the same project:
+
+- Child pipelines still execute each of their jobs according to a stage sequence, but
+  would be free to continue forward through their stages without waiting for unrelated
+  jobs in the parent pipeline to finish.
+- The configuration is split up into smaller child pipeline configurations, which are
+  easier to understand. This reduces the cognitive load to understand the overall configuration.
+- Imports are done at the child pipeline level, reducing the likelihood of collisions.
+- Each pipeline has only the steps relevant steps, making it easier to understand what's going on.
+
+Child pipelines work well with other GitLab CI features:
+
+- Use [`only: changes`](yaml/README.md#onlychangesexceptchanges) to trigger pipelines only when
+  certain files change. This is useful for monorepos, for example.
+- Since the parent pipeline in `.gitlab-ci.yml` and the child pipeline run as normal
+  pipelines, they can have their own behaviors and sequencing in relation to triggers.
+
+All of this will work with [`include:`](yaml/README.md#include) feature so you can compose
+the child pipeline configuration.
+
+## Examples
+
+The simplest case is [triggering a child pipeline](yaml/README.md#trigger-premium) using a
+local YAML file to define the pipeline configuration. In this case, the parent pipeline will
+trigger the child pipeline, and continue without waiting:
+
+```yaml
+microservice_a:
+  trigger:
+    include: path/to/microservice_a.yml
+```
+
+You can include multiple files when composing a child pipeline:
+
+```yaml
+microservice_a:
+  trigger:
+    include:
+      - local: path/to/microservice_a.yml
+      - template: SAST.gitlab-ci.yml
+```
+
+NOTE: **Note:**
+The max number of entries that are accepted for `trigger:include:` is three.
+
+Similar to [multi-project pipelines](multi_project_pipelines.md#mirroring-status-from-triggered-pipeline),
+we can set the parent pipeline to depend on the status of the child pipeline upon completion:
+
+```yaml
+microservice_a:
+  trigger:
+    include:
+      - local: path/to/microservice_a.yml
+      - template: SAST.gitlab-ci.yml
+    strategy: depend
+```
+
+## Limitations
+
+A parent pipeline can trigger many child pipelines, but a child pipeline cannot trigger
+further child pipelines. See the [related issue](https://gitlab.com/gitlab-org/gitlab/issues/29651) for discussion on possible future improvements.
--- a/doc/ci/pipelines.md
+++ b/doc/ci/pipelines.md
@ -246,6 +246,13 @@ Pipelines for different projects can be combined and visualized together.

 For more information, see [Multi-project pipelines](multi_project_pipelines.md).

+## Parent-child pipelines
+
+Complex pipelines can be broken down into one parent pipeline that can trigger
+multiple child sub-pipelines, which all run in the same project and with the same SHA.
+
+For more information, see [Parent-Child pipelines](parent_child_pipelines.md).
+
 ## Working with pipelines

 In general, pipelines are executed automatically and require no intervention once created.
--- a/doc/ci/yaml/README.md
+++ b/doc/ci/yaml/README.md
@ -2600,14 +2600,17 @@ job split into three separate jobs.
 from `trigger` definition is started by GitLab, a downstream pipeline gets
 created.

-Learn more about [multi-project pipelines](../multi_project_pipelines.md#creating-multi-project-pipelines-from-gitlab-ciyml).
+This keyword allows the creation of two different types of downstream pipelines:
+
+- [Multi-project pipelines](../multi_project_pipelines.md#creating-multi-project-pipelines-from-gitlab-ciyml)
+- [Child pipelines](../parent_child_pipelines.md)

 NOTE: **Note:**
 Using a `trigger` with `when:manual` together results in the error `jobs:#{job-name}
 when should be on_success, on_failure or always`, because `when:manual` prevents
 triggers being used.

-#### Simple `trigger` syntax
+#### Simple `trigger` syntax for multi-project pipelines

 The simplest way to configure a downstream trigger is to use `trigger` keyword
 with a full path to a downstream project:
@ -2622,7 +2625,7 @@ staging:
  trigger: my/deployment
 ```

-#### Complex `trigger` syntax
+#### Complex `trigger` syntax for multi-project pipelines

 It is possible to configure a branch name that GitLab will use to create
 a downstream pipeline with:
@ -2657,6 +2660,28 @@ upstream_bridge:
    pipeline: other/project
 ```

+#### `trigger` syntax for child pipeline
+
+To create a [child pipeline](../parent_child_pipelines.md), specify the path to the
+YAML file containing the CI config of the child pipeline:
+
+```yaml
+trigger_job:
+  trigger:
+    include: path/to/child-pipeline.yml
+```
+
+Similar to [multi-project pipelines](../multi_project_pipelines.md#mirroring-status-from-triggered-pipeline),
+it is possible to mirror the status from a triggered pipeline:
+
+```yaml
+trigger_job:
+  trigger:
+    include:
+      - local: path/to/child-pipeline.yml
+    strategy: depend
+```
+
 ### `interruptible`

 > [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/merge_requests/23464) in GitLab 12.3.
--- a/lib/gitlab/background_migration/activate_prometheus_services_for_shared_cluster_applications.rb
+++ b/lib/gitlab/background_migration/activate_prometheus_services_for_shared_cluster_applications.rb
@ -1,52 +0,0 @@
-# frozen_string_literal: true
-
-module Gitlab
-  module BackgroundMigration
-    # Create missing PrometheusServices records or sets active attribute to true
-    # for all projects which belongs to cluster with Prometheus Application installed.
-    class ActivatePrometheusServicesForSharedClusterApplications
-      module Migratable
-        # Migration model namespace isolated from application code.
-        class PrometheusService < ActiveRecord::Base
-          self.inheritance_column = :_type_disabled
-          self.table_name = 'services'
-
-          default_scope { where("services.type = 'PrometheusService'") }
-
-          def self.for_project(project_id)
-            new(
-              project_id: project_id,
-              active: true,
-              properties: '{}',
-              type: 'PrometheusService',
-              template: false,
-              push_events: true,
-              issues_events: true,
-              merge_requests_events: true,
-              tag_push_events: true,
-              note_events: true,
-              category: 'monitoring',
-              default: false,
-              wiki_page_events: true,
-              pipeline_events: true,
-              confidential_issues_events: true,
-              commit_events: true,
-              job_events: true,
-              confidential_note_events: true,
-              deployment_events: false
-            )
-          end
-
-          def managed?
-            properties == '{}'
-          end
-        end
-      end
-
-      def perform(project_id)
-        service = Migratable::PrometheusService.find_by(project_id: project_id) || Migratable::PrometheusService.for_project(project_id)
-        service.update!(active: true) if service.managed?
-      end
-    end
-  end
-end
--- a/lib/gitlab/ci/pipeline/chain/command.rb
+++ b/lib/gitlab/ci/pipeline/chain/command.rb
@ -22,12 +22,6 @@ module Gitlab
            end
          end

-          def uses_unsupported_legacy_trigger?
-            trigger_request.present? &&
-              trigger_request.trigger.legacy? &&
-              !trigger_request.trigger.supports_legacy_tokens?
-          end
-
          def branch_exists?
            strong_memoize(:is_branch) do
              project.repository.branch_exists?(ref)
--- a/lib/gitlab/ci/pipeline/chain/validate/abilities.rb
+++ b/lib/gitlab/ci/pipeline/chain/validate/abilities.rb
@ -14,16 +14,12 @@ module Gitlab
                return error('Pipelines are disabled!')
              end

-              if @command.uses_unsupported_legacy_trigger?
-                return error('Trigger token is invalid because is not owned by any user')
+              unless allowed_to_create_pipeline?
+                return error('Insufficient permissions to create a new pipeline')
              end

-              unless allowed_to_trigger_pipeline?
-                if can?(current_user, :create_pipeline, project)
-                  return error("Insufficient permissions for protected ref '#{command.ref}'")
-                else
-                  return error('Insufficient permissions to create a new pipeline')
-                end
+              unless allowed_to_write_ref?
+                return error("Insufficient permissions for protected ref '#{command.ref}'")
              end
            end

@ -31,17 +27,13 @@ module Gitlab
              @pipeline.errors.any?
            end

-            def allowed_to_trigger_pipeline?
-              if current_user
-                allowed_to_create?
-              else # legacy triggers don't have a corresponding user
-                !@command.protected_ref?
-              end
+            private
+
+            def allowed_to_create_pipeline?
+              can?(current_user, :create_pipeline, project)
            end

-            def allowed_to_create?
-              return unless can?(current_user, :create_pipeline, project)
-
+            def allowed_to_write_ref?
              access = Gitlab::UserAccess.new(current_user, project: project)

              if @command.branch_exists?
--- a/lib/gitlab/import_export/group_project_object_builder.rb
+++ b/lib/gitlab/import_export/group_project_object_builder.rb
@ -26,6 +26,8 @@ module Gitlab
      end

      def find
+        return if epic? && group.nil?
+
        find_object || klass.create(project_attributes)
      end

@ -54,10 +56,10 @@ module Gitlab
      # or, if group is present:
      # `"{table_name}"."project_id" = {project.id} OR "{table_name}"."group_id" = {group.id}`
      def where_clause_base
-        clause = table[:project_id].eq(project.id) if project
-        clause = clause.or(table[:group_id].eq(group.id)) if group
-
-        clause
+        [].tap do |clauses|
+          clauses << table[:project_id].eq(project.id) if project
+          clauses << table[:group_id].eq(group.id) if group
+        end.reduce(:or)
      end

      # Returns Arel clause `"{table_name}"."title" = '{attributes['title']}'`
@ -108,6 +110,10 @@ module Gitlab
        klass == MergeRequest
      end

+      def epic?
+        klass == Epic
+      end
+
      # If an existing group milestone used the IID
      # claim the IID back and set the group milestone to use one available
      # This is necessary to fix situations like the following:
--- a/lib/gitlab/import_export/import_export.yml
+++ b/lib/gitlab/import_export/import_export.yml
@ -322,6 +322,13 @@ excluded_attributes:
    - :board_id
    - :label_id
    - :milestone_id
+  epic:
+    - :start_date_sourcing_milestone_id
+    - :due_date_sourcing_milestone_id
+    - :parent_id
+    - :state_id
+    - :start_date_sourcing_epic_id
+    - :due_date_sourcing_epic_id
 methods:
  notes:
    - :type
@ -374,6 +381,7 @@ ee:
        - design_versions:
          - actions:
            - :design # Duplicate export of issues.designs in order to link the record to both Issue and Action
+        - :epic
      - protected_branches:
        - :unprotect_access_levels
      - protected_environments:
--- a/lib/gitlab/import_export/relation_factory.rb
+++ b/lib/gitlab/import_export/relation_factory.rb
@ -40,7 +40,21 @@ module Gitlab

      IMPORTED_OBJECT_MAX_RETRIES = 5.freeze

-      EXISTING_OBJECT_CHECK = %i[milestone milestones label labels project_label project_labels group_label group_labels project_feature merge_request ProjectCiCdSetting container_expiration_policy].freeze
+      EXISTING_OBJECT_CHECK = %i[
+        milestone
+        milestones
+        label
+        labels
+        project_label
+        project_labels
+        group_label
+        group_labels
+        project_feature
+        merge_request
+        epic
+        ProjectCiCdSetting
+        container_expiration_policy
+      ].freeze

      TOKEN_RESET_MODELS = %i[Project Namespace Ci::Trigger Ci::Build Ci::Runner ProjectHook].freeze

@ -86,9 +100,6 @@ module Gitlab
      def create
        return if unknown_service?

-        # Do not import legacy triggers
-        return if !Feature.enabled?(:use_legacy_pipeline_triggers, @project) && legacy_trigger?
-
        setup_models

        object = generate_imported_object
@ -345,10 +356,6 @@ module Gitlab
          !Object.const_defined?(parsed_relation_hash['type'])
      end

-      def legacy_trigger?
-        @relation_name == :'Ci::Trigger' && @relation_hash['owner_id'].nil?
-      end
-
      def find_or_create_object!
        if UNIQUE_RELATIONS.include?(@relation_name)
          unique_relation_object = relation_class.find_or_create_by(project_id: @project.id)
--- a/lib/gitlab/import_export/relation_tree_restorer.rb
+++ b/lib/gitlab/import_export/relation_tree_restorer.rb
@ -4,7 +4,7 @@ module Gitlab
  module ImportExport
    class RelationTreeRestorer
      # Relations which cannot be saved at project level (and have a group assigned)
-      GROUP_MODELS = [GroupLabel, Milestone].freeze
+      GROUP_MODELS = [GroupLabel, Milestone, Epic].freeze

      attr_reader :user
      attr_reader :shared
--- a/package.json
+++ b/package.json
@ -82,6 +82,7 @@
    "fuzzaldrin-plus": "^0.5.0",
    "glob": "^7.1.2",
    "graphql": "^14.0.2",
+    "immer": "^5.2.1",
    "imports-loader": "^0.8.0",
    "jed": "^1.1.1",
    "jest-transform-graphql": "^2.1.0",
--- a/qa/qa/page/project/web_ide/edit.rb
+++ b/qa/qa/page/project/web_ide/edit.rb
@ -108,9 +108,9 @@ module QA
            # Click :commit_button and keep retrying just in case part of the
            # animation is still in process even when the buttons have the
            # expected visibility.
-            commit_success_msg_shown = retry_until do
-              click_element :commit_to_current_branch_radio
-              click_element :commit_button
+            commit_success_msg_shown = retry_until(sleep_interval: 5) do
+              click_element(:commit_to_current_branch_radio) if has_element?(:commit_to_current_branch_radio)
+              click_element(:commit_button) if has_element?(:commit_button)

              wait(reload: false) do
                has_text?('Your changes have been committed')
--- a/spec/controllers/admin/sessions_controller_spec.rb
+++ b/spec/controllers/admin/sessions_controller_spec.rb
@ -122,7 +122,7 @@ describe Admin::SessionsController, :do_not_mock_admin_mode do
  describe '#destroy' do
    context 'for regular users' do
      it 'shows error page' do
-        get :destroy
+        post :destroy

        expect(response).to have_gitlab_http_status(404)
        expect(controller.current_user_mode.admin_mode?).to be(false)
@ -139,7 +139,7 @@ describe Admin::SessionsController, :do_not_mock_admin_mode do
        post :create, params: { password: user.password }
        expect(controller.current_user_mode.admin_mode?).to be(true)

-        get :destroy
+        post :destroy

        expect(response).to have_gitlab_http_status(:found)
        expect(response).to redirect_to(root_path)
--- a/spec/features/merge_request/maintainer_edits_fork_spec.rb
+++ b/spec/features/merge_request/maintainer_edits_fork_spec.rb
@ -32,8 +32,6 @@ describe 'a maintainer edits files on a source-branch of an MR from a fork', :js
    wait_for_requests
  end

-  it_behaves_like 'rendering a single diff version'
-
  it 'mentions commits will go to the source branch' do
    expect(page).to have_content('Your changes can be committed to fix because a merge request is open.')
  end
--- a/spec/features/merge_request/user_comments_on_diff_spec.rb
+++ b/spec/features/merge_request/user_comments_on_diff_spec.rb
@ -13,15 +13,12 @@ describe 'User comments on a diff', :js do
  let(:user) { create(:user) }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    project.add_maintainer(user)
    sign_in(user)

    visit(diffs_project_merge_request_path(project, merge_request))
  end

-  it_behaves_like 'rendering a single diff version'
-
  context 'when viewing comments' do
    context 'when toggling inline comments' do
      context 'in a single file' do
--- a/spec/features/merge_request/user_creates_image_diff_notes_spec.rb
+++ b/spec/features/merge_request/user_creates_image_diff_notes_spec.rb
@ -9,7 +9,6 @@ describe 'Merge request > User creates image diff notes', :js do
  let(:user) { project.creator }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    sign_in(user)

    # Stub helper to return any blob file as image from public app folder.
@ -18,8 +17,6 @@ describe 'Merge request > User creates image diff notes', :js do
    allow_any_instance_of(DiffHelper).to receive(:diff_file_old_blob_raw_url).and_return('/favicon.png')
  end

-  it_behaves_like 'rendering a single diff version'
-
  context 'create commit diff notes' do
    commit_id = '2f63565e7aac07bcdadb654e253078b727143ec4'

--- a/spec/features/merge_request/user_expands_diff_spec.rb
+++ b/spec/features/merge_request/user_expands_diff_spec.rb
@ -7,7 +7,6 @@ describe 'User expands diff', :js do
  let(:merge_request) { create(:merge_request, source_branch: 'expand-collapse-files', source_project: project, target_project: project) }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    stub_feature_flags(diffs_batch_load: false)

    allow(Gitlab::Git::Diff).to receive(:size_limit).and_return(100.kilobytes)
@ -18,8 +17,6 @@ describe 'User expands diff', :js do
    wait_for_requests
  end

-  it_behaves_like 'rendering a single diff version'
-
  it 'allows user to expand diff' do
    page.within find('[id="6eb14e00385d2fb284765eb1cd8d420d33d63fc9"]') do
      click_link 'Click to expand it.'
--- a/spec/features/merge_request/user_posts_diff_notes_spec.rb
+++ b/spec/features/merge_request/user_posts_diff_notes_spec.rb
@ -14,15 +14,12 @@ describe 'Merge request > User posts diff notes', :js do
  let(:test_note_comment) { 'this is a test note!' }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    set_cookie('sidebar_collapsed', 'true')

    project.add_developer(user)
    sign_in(user)
  end

-  it_behaves_like 'rendering a single diff version'
-
  context 'when hovering over a parallel view diff file' do
    before do
      visit diffs_project_merge_request_path(project, merge_request, view: 'parallel')
--- a/spec/features/merge_request/user_posts_notes_spec.rb
+++ b/spec/features/merge_request/user_posts_notes_spec.rb
@ -165,9 +165,9 @@ describe 'Merge request > User posts notes', :js do
        find('.js-note-edit').click

        page.within('.current-note-edit-form') do
-          expect(find('#note_note').value).to eq('This is the new content')
+          expect(find('#note_note').value).to include('This is the new content')
          first('.js-md').click
-          expect(find('#note_note').value).to eq('This is the new content****')
+          expect(find('#note_note').value).to include('This is the new content****')
        end
      end

--- a/spec/features/merge_request/user_resolves_conflicts_spec.rb
+++ b/spec/features/merge_request/user_resolves_conflicts_spec.rb
@ -9,7 +9,6 @@ describe 'Merge request > User resolves conflicts', :js do
  before do
    # In order to have the diffs collapsed, we need to disable the increase feature
    stub_feature_flags(gitlab_git_diff_size_limit_increase: false)
-    stub_feature_flags(single_mr_diff_view: false)
  end

  def create_merge_request(source_branch)
@ -18,8 +17,6 @@ describe 'Merge request > User resolves conflicts', :js do
    end
  end

-  it_behaves_like 'rendering a single diff version'
-
  shared_examples 'conflicts are resolved in Interactive mode' do
    it 'conflicts are resolved in Interactive mode' do
      within find('.files-wrapper .diff-file', text: 'files/ruby/popen.rb') do
--- a/spec/features/merge_request/user_resolves_diff_notes_and_discussions_resolve_spec.rb
+++ b/spec/features/merge_request/user_resolves_diff_notes_and_discussions_resolve_spec.rb
@ -20,12 +20,9 @@ describe 'Merge request > User resolves diff notes and threads', :js do
  end

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    stub_feature_flags(diffs_batch_load: false)
  end

-  it_behaves_like 'rendering a single diff version'
-
  context 'no threads' do
    before do
      project.add_maintainer(user)
--- a/spec/features/merge_request/user_sees_avatar_on_diff_notes_spec.rb
+++ b/spec/features/merge_request/user_sees_avatar_on_diff_notes_spec.rb
@ -21,7 +21,6 @@ describe 'Merge request > User sees avatars on diff notes', :js do
  let!(:note) { create(:diff_note_on_merge_request, project: project, noteable: merge_request, position: position) }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    stub_feature_flags(diffs_batch_load: false)
    project.add_maintainer(user)
    sign_in user
@ -29,8 +28,6 @@ describe 'Merge request > User sees avatars on diff notes', :js do
    set_cookie('sidebar_collapsed', 'true')
  end

-  it_behaves_like 'rendering a single diff version'
-
  context 'discussion tab' do
    before do
      visit project_merge_request_path(project, merge_request)
--- a/spec/features/merge_request/user_sees_diff_spec.rb
+++ b/spec/features/merge_request/user_sees_diff_spec.rb
@ -10,12 +10,9 @@ describe 'Merge request > User sees diff', :js do
  let(:merge_request) { create(:merge_request, source_project: project) }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    stub_feature_flags(diffs_batch_load: false)
  end

-  it_behaves_like 'rendering a single diff version'
-
  context 'when linking to note' do
    describe 'with unresolved note' do
      let(:note) { create :diff_note_on_merge_request, project: project, noteable: merge_request }
--- a/spec/features/merge_request/user_sees_mr_with_deleted_source_branch_spec.rb
+++ b/spec/features/merge_request/user_sees_mr_with_deleted_source_branch_spec.rb
@ -11,14 +11,11 @@ describe 'Merge request > User sees MR with deleted source branch', :js do
  let(:user) { project.creator }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    merge_request.update!(source_branch: 'this-branch-does-not-exist')
    sign_in(user)
    visit project_merge_request_path(project, merge_request)
  end

-  it_behaves_like 'rendering a single diff version'
-
  it 'shows a message about missing source branch' do
    expect(page).to have_content('Source branch does not exist.')
  end
--- a/spec/features/merge_request/user_sees_versions_spec.rb
+++ b/spec/features/merge_request/user_sees_versions_spec.rb
@ -16,7 +16,6 @@ describe 'Merge request > User sees versions', :js do
  let!(:params) { {} }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    stub_feature_flags(diffs_batch_load: false)

    project.add_maintainer(user)
@ -24,8 +23,6 @@ describe 'Merge request > User sees versions', :js do
    visit diffs_project_merge_request_path(project, merge_request, params)
  end

-  it_behaves_like 'rendering a single diff version'
-
  shared_examples 'allows commenting' do |file_id:, line_code:, comment:|
    it do
      diff_file_selector = ".diff-file[id='#{file_id}']"
--- a/spec/features/merge_request/user_suggests_changes_on_diff_spec.rb
+++ b/spec/features/merge_request/user_suggests_changes_on_diff_spec.rb
@ -25,15 +25,12 @@ describe 'User comments on a diff', :js do
  let(:user) { create(:user) }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    project.add_maintainer(user)
    sign_in(user)

    visit(diffs_project_merge_request_path(project, merge_request))
  end

-  it_behaves_like 'rendering a single diff version'
-
  context 'single suggestion note' do
    it 'hides suggestion popover' do
      click_diff_line(find("[id='#{sample_compare.changes[1][:line_code]}']"))
--- a/spec/features/merge_request/user_toggles_whitespace_changes_spec.rb
+++ b/spec/features/merge_request/user_toggles_whitespace_changes_spec.rb
@ -8,7 +8,6 @@ describe 'Merge request > User toggles whitespace changes', :js do
  let(:user) { project.creator }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    project.add_maintainer(user)
    sign_in(user)
    visit diffs_project_merge_request_path(project, merge_request)
@ -16,8 +15,6 @@ describe 'Merge request > User toggles whitespace changes', :js do
    find('.js-show-diff-settings').click
  end

-  it_behaves_like 'rendering a single diff version'
-
  it 'has a button to toggle whitespace changes' do
    expect(page).to have_content 'Show whitespace changes'
  end
--- a/spec/features/merge_request/user_views_diffs_spec.rb
+++ b/spec/features/merge_request/user_views_diffs_spec.rb
@ -9,7 +9,6 @@ describe 'User views diffs', :js do
  let(:project) { create(:project, :public, :repository) }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    stub_feature_flags(diffs_batch_load: false)
    visit(diffs_project_merge_request_path(project, merge_request))

@ -18,8 +17,6 @@ describe 'User views diffs', :js do
    find('.js-toggle-tree-list').click
  end

-  it_behaves_like 'rendering a single diff version'
-
  shared_examples 'unfold diffs' do
    it 'unfolds diffs upwards' do
      first('.js-unfold').click
--- a/spec/features/projects/blobs/edit_spec.rb
+++ b/spec/features/projects/blobs/edit_spec.rb
@ -12,11 +12,9 @@ describe 'Editing file blob', :js do
  let(:readme_file_path) { 'README.md' }

  before do
-    stub_feature_flags(web_ide_default: false, single_mr_diff_view: false)
+    stub_feature_flags(web_ide_default: false)
  end

-  it_behaves_like 'rendering a single diff version'
-
  context 'as a developer' do
    let(:user) { create(:user) }
    let(:role) { :developer }
--- a/spec/features/projects/view_on_env_spec.rb
+++ b/spec/features/projects/view_on_env_spec.rb
@ -9,14 +9,11 @@ describe 'View on environment', :js do
  let(:user) { project.creator }

  before do
-    stub_feature_flags(single_mr_diff_view: false)
    stub_feature_flags(diffs_batch_load: false)

    project.add_maintainer(user)
  end

-  it_behaves_like 'rendering a single diff version'
-
  context 'when the branch has a route map' do
    let(:route_map) do
      <<-MAP.strip_heredoc
--- a/spec/features/triggers_spec.rb
+++ b/spec/features/triggers_spec.rb
@ -65,22 +65,6 @@ describe 'Triggers', :js do
      expect(page.find('.triggers-list')).to have_content new_trigger_title
      expect(page.find('.triggers-list .trigger-owner')).to have_content user.name
    end
-
-    it 'edit "legacy" trigger and save' do
-      # Create new trigger without owner association, i.e. Legacy trigger
-      create(:ci_trigger, owner: user, project: @project).update_attribute(:owner, nil)
-      visit project_settings_ci_cd_path(@project)
-
-      # See if the trigger can be edited and description is blank
-      find('a[title="Edit"]').send_keys(:return)
-      expect(page.find('#trigger_description').value).to have_content ''
-
-      # See if trigger can be updated with description and saved successfully
-      fill_in 'trigger_description', with: new_trigger_title
-      click_button 'Save trigger'
-      expect(page.find('.flash-notice')).to have_content 'Trigger was successfully updated.'
-      expect(page.find('.triggers-list')).to have_content new_trigger_title
-    end
  end

  describe 'trigger "Revoke" workflow' do
@ -106,43 +90,18 @@ describe 'Triggers', :js do
  end

  describe 'show triggers workflow' do
-    before do
-      stub_feature_flags(use_legacy_pipeline_triggers: false)
-    end
-
    it 'contains trigger description placeholder' do
      expect(page.find('#trigger_description')['placeholder']).to eq 'Trigger description'
    end

-    it 'show "invalid" badge for legacy trigger' do
-      create(:ci_trigger, owner: user, project: @project).update_attribute(:owner, nil)
-      visit project_settings_ci_cd_path(@project)
-
-      expect(page.find('.triggers-list')).to have_content 'invalid'
-    end
-
    it 'show "invalid" badge for trigger with owner having insufficient permissions' do
      create(:ci_trigger, owner: guest_user, project: @project, description: trigger_title)
      visit project_settings_ci_cd_path(@project)

-      # See if trigger without owner (i.e. legacy) shows "legacy" badge and is non-editable
      expect(page.find('.triggers-list')).to have_content 'invalid'
      expect(page.find('.triggers-list')).not_to have_selector('a[title="Edit"]')
    end

-    it 'do not show "Edit" or full token for legacy trigger' do
-      create(:ci_trigger, owner: user, project: @project, description: trigger_title)
-        .update_attribute(:owner, nil)
-      visit project_settings_ci_cd_path(@project)
-
-      # See if trigger not owned shows only first few token chars and doesn't have copy-to-clipboard button
-      expect(page.find('.triggers-list')).to have_content(@project.triggers.first.token[0..3])
-      expect(page.find('.triggers-list')).not_to have_selector('button.btn-clipboard')
-
-      # See if trigger is non-editable
-      expect(page.find('.triggers-list')).not_to have_selector('a[title="Edit"]')
-    end
-
    it 'do not show "Edit" or full token for not owned trigger' do
      # Create trigger with user different from current_user
      create(:ci_trigger, owner: user2, project: @project, description: trigger_title)
@ -169,56 +128,5 @@ describe 'Triggers', :js do
      expect(page.find('.triggers-list .trigger-owner')).to have_content user.name
      expect(page.find('.triggers-list')).to have_selector('a[title="Edit"]')
    end
-
-    context 'when :use_legacy_pipeline_triggers feature flag is enabled' do
-      before do
-        stub_feature_flags(use_legacy_pipeline_triggers: true)
-      end
-
-      it 'show "legacy" badge for legacy trigger' do
-        create(:ci_trigger, owner: nil, project: @project)
-        visit project_settings_ci_cd_path(@project)
-
-        # See if trigger without owner (i.e. legacy) shows "legacy" badge and is editable
-        expect(page.find('.triggers-list')).to have_content 'legacy'
-        expect(page.find('.triggers-list')).to have_selector('a[title="Edit"]')
-      end
-
-      it 'show "invalid" badge for trigger with owner having insufficient permissions' do
-        create(:ci_trigger, owner: guest_user, project: @project, description: trigger_title)
-        visit project_settings_ci_cd_path(@project)
-
-        # See if trigger without owner (i.e. legacy) shows "legacy" badge and is non-editable
-        expect(page.find('.triggers-list')).to have_content 'invalid'
-        expect(page.find('.triggers-list')).not_to have_selector('a[title="Edit"]')
-      end
-
-      it 'do not show "Edit" or full token for not owned trigger' do
-        # Create trigger with user different from current_user
-        create(:ci_trigger, owner: user2, project: @project, description: trigger_title)
-        visit project_settings_ci_cd_path(@project)
-
-        # See if trigger not owned by current_user shows only first few token chars and doesn't have copy-to-clipboard button
-        expect(page.find('.triggers-list')).to have_content(@project.triggers.first.token[0..3])
-        expect(page.find('.triggers-list')).not_to have_selector('button.btn-clipboard')
-
-        # See if trigger owner name doesn't match with current_user and trigger is non-editable
-        expect(page.find('.triggers-list .trigger-owner')).not_to have_content user.name
-        expect(page.find('.triggers-list')).not_to have_selector('a[title="Edit"]')
-      end
-
-      it 'show "Edit" and full token for owned trigger' do
-        create(:ci_trigger, owner: user, project: @project, description: trigger_title)
-        visit project_settings_ci_cd_path(@project)
-
-        # See if trigger shows full token and has copy-to-clipboard button
-        expect(page.find('.triggers-list')).to have_content @project.triggers.first.token
-        expect(page.find('.triggers-list')).to have_selector('button.btn-clipboard')
-
-        # See if trigger owner name matches with current_user and is editable
-        expect(page.find('.triggers-list .trigger-owner')).to have_content user.name
-        expect(page.find('.triggers-list')).to have_selector('a[title="Edit"]')
-      end
-    end
  end
 end
--- a/spec/fixtures/lib/gitlab/import_export/group/project.json
+++ b/spec/fixtures/lib/gitlab/import_export/group/project.json
@ -175,6 +175,67 @@
          }
        }
      ]
+    },
+    {
+      "id": 3,
+      "title": "Issue with Epic",
+      "author_id": 1,
+      "project_id": 8,
+      "created_at": "2019-12-08T19:41:11.233Z",
+      "updated_at": "2019-12-08T19:41:53.194Z",
+      "position": 0,
+      "branch_name": null,
+      "description": "Donec at nulla vitae sem molestie rutrum ut at sem.",
+      "state": "opened",
+      "iid": 3,
+      "updated_by_id": null,
+      "confidential": false,
+      "due_date": null,
+      "moved_to_id": null,
+      "issue_assignees": [],
+      "notes": [],
+      "milestone": {
+        "id": 2,
+        "title": "A group milestone",
+        "description": "Group-level milestone",
+        "due_date": null,
+        "created_at": "2016-06-14T15:02:04.415Z",
+        "updated_at": "2016-06-14T15:02:04.415Z",
+        "state": "active",
+        "iid": 1,
+        "group_id": 100
+      },
+      "epic": {
+        "id": 1,
+        "group_id": 5,
+        "author_id": 1,
+        "assignee_id": null,
+        "iid": 1,
+        "updated_by_id": null,
+        "last_edited_by_id": null,
+        "lock_version": 0,
+        "start_date": null,
+        "end_date": null,
+        "last_edited_at": null,
+        "created_at": "2019-12-08T19:37:07.098Z",
+        "updated_at": "2019-12-08T19:43:11.568Z",
+        "title": "An epic",
+        "description": null,
+        "start_date_sourcing_milestone_id": null,
+        "due_date_sourcing_milestone_id": null,
+        "start_date_fixed": null,
+        "due_date_fixed": null,
+        "start_date_is_fixed": null,
+        "due_date_is_fixed": null,
+        "closed_by_id": null,
+        "closed_at": null,
+        "parent_id": null,
+        "relative_position": null,
+        "state_id": "opened",
+        "start_date_sourcing_epic_id": null,
+        "due_date_sourcing_epic_id": null,
+        "milestone_id": null
+      }
    }
  ],
  "snippets": [
--- a/spec/frontend/error_tracking/components/error_details_spec.js
+++ b/spec/frontend/error_tracking/components/error_details_spec.js
@ -13,6 +13,7 @@ describe('ErrorDetails', () => {
  let wrapper;
  let actions;
  let getters;
+  let mocks;

  const findInput = name => {
    const inputs = wrapper.findAll(GlFormInput).filter(c => c.attributes('name') === name);
@ -24,13 +25,27 @@ describe('ErrorDetails', () => {
      stubs: { LoadingButton },
      localVue,
      store,
+      mocks,
      propsData: {
+        issueId: '123',
+        projectPath: '/root/gitlab-test',
        issueDetailsPath: '/123/details',
        issueStackTracePath: '/stacktrace',
        projectIssuesPath: '/test-project/issues/',
        csrfToken: 'fakeToken',
      },
    });
+    wrapper.setData({
+      GQLerror: {
+        id: 129381,
+        title: 'Issue title',
+        externalUrl: 'http://sentry.gitlab.net/gitlab',
+        firstSeen: '2017-05-26T13:32:48Z',
+        lastSeen: '2018-05-26T13:32:48Z',
+        count: 12,
+        userCount: 2,
+      },
+    });
  }

  beforeEach(() => {
@ -61,6 +76,19 @@ describe('ErrorDetails', () => {
        },
      },
    });
+
+    const query = jest.fn();
+    mocks = {
+      $apollo: {
+        query,
+        queries: {
+          GQLerror: {
+            loading: true,
+            stopPolling: jest.fn(),
+          },
+        },
+      },
+    };
  });

  afterEach(() => {
@ -85,10 +113,11 @@ describe('ErrorDetails', () => {
    beforeEach(() => {
      store.state.details.loading = false;
      store.state.details.error.id = 1;
+      mocks.$apollo.queries.GQLerror.loading = false;
+      mountComponent();
    });

    it('should show Sentry error details without stacktrace', () => {
-      mountComponent();
      expect(wrapper.find(GlLink).exists()).toBe(true);
      expect(wrapper.find(GlLoadingIcon).exists()).toBe(true);
      expect(wrapper.find(Stacktrace).exists()).toBe(false);
@ -99,13 +128,17 @@ describe('ErrorDetails', () => {
      it('should show language and error level badges', () => {
        store.state.details.error.tags = { level: 'error', logger: 'ruby' };
        mountComponent();
-        expect(wrapper.findAll(GlBadge).length).toBe(2);
+        return wrapper.vm.$nextTick().then(() => {
+          expect(wrapper.findAll(GlBadge).length).toBe(2);
+        });
      });

      it('should NOT show the badge if the tag is not present', () => {
        store.state.details.error.tags = { level: 'error' };
        mountComponent();
-        expect(wrapper.findAll(GlBadge).length).toBe(1);
+        return wrapper.vm.$nextTick().then(() => {
+          expect(wrapper.findAll(GlBadge).length).toBe(1);
+        });
      });
    });

@ -113,8 +146,10 @@ describe('ErrorDetails', () => {
      it('should show stacktrace', () => {
        store.state.details.loadingStacktrace = false;
        mountComponent();
-        expect(wrapper.find(GlLoadingIcon).exists()).toBe(false);
-        expect(wrapper.find(Stacktrace).exists()).toBe(true);
+        return wrapper.vm.$nextTick().then(() => {
+          expect(wrapper.find(GlLoadingIcon).exists()).toBe(false);
+          expect(wrapper.find(Stacktrace).exists()).toBe(true);
+        });
      });

      it('should NOT show stacktrace if no entries', () => {
@ -128,15 +163,6 @@ describe('ErrorDetails', () => {

    describe('When a user clicks the create issue button', () => {
      beforeEach(() => {
-        store.state.details.error = {
-          id: 129381,
-          title: 'Issue title',
-          external_url: 'http://sentry.gitlab.net/gitlab',
-          first_seen: '2017-05-26T13:32:48Z',
-          last_seen: '2018-05-26T13:32:48Z',
-          count: 12,
-          user_count: 2,
-        };
        mountComponent();
      });

--- a/spec/frontend/helpers/diffs_helper_spec.js
+++ b/spec/frontend/helpers/diffs_helper_spec.js
@ -0,0 +1,113 @@
+import * as diffsHelper from '~/helpers/diffs_helper';
+
+describe('diffs helper', () => {
+  function getDiffFile(withOverrides = {}) {
+    return {
+      parallel_diff_lines: ['line'],
+      highlighted_diff_lines: ['line'],
+      blob: {
+        readable_text: 'text',
+      },
+      ...withOverrides,
+    };
+  }
+
+  describe('hasInlineLines', () => {
+    it('is false when the file does not exist', () => {
+      expect(diffsHelper.hasInlineLines()).toBeFalsy();
+    });
+
+    it('is false when the file does not have the highlighted_diff_lines property', () => {
+      const missingInline = getDiffFile({ highlighted_diff_lines: undefined });
+
+      expect(diffsHelper.hasInlineLines(missingInline)).toBeFalsy();
+    });
+
+    it('is false when the file has zero highlighted_diff_lines', () => {
+      const emptyInline = getDiffFile({ highlighted_diff_lines: [] });
+
+      expect(diffsHelper.hasInlineLines(emptyInline)).toBeFalsy();
+    });
+
+    it('is true when the file has at least 1 highlighted_diff_lines', () => {
+      expect(diffsHelper.hasInlineLines(getDiffFile())).toBeTruthy();
+    });
+  });
+
+  describe('hasParallelLines', () => {
+    it('is false when the file does not exist', () => {
+      expect(diffsHelper.hasParallelLines()).toBeFalsy();
+    });
+
+    it('is false when the file does not have the parallel_diff_lines property', () => {
+      const missingInline = getDiffFile({ parallel_diff_lines: undefined });
+
+      expect(diffsHelper.hasParallelLines(missingInline)).toBeFalsy();
+    });
+
+    it('is false when the file has zero parallel_diff_lines', () => {
+      const emptyInline = getDiffFile({ parallel_diff_lines: [] });
+
+      expect(diffsHelper.hasParallelLines(emptyInline)).toBeFalsy();
+    });
+
+    it('is true when the file has at least 1 parallel_diff_lines', () => {
+      expect(diffsHelper.hasParallelLines(getDiffFile())).toBeTruthy();
+    });
+  });
+
+  describe('isSingleViewStyle', () => {
+    it('is true when the file has at least 1 inline line but no parallel lines for any reason', () => {
+      const noParallelLines = getDiffFile({ parallel_diff_lines: undefined });
+      const emptyParallelLines = getDiffFile({ parallel_diff_lines: [] });
+
+      expect(diffsHelper.isSingleViewStyle(noParallelLines)).toBeTruthy();
+      expect(diffsHelper.isSingleViewStyle(emptyParallelLines)).toBeTruthy();
+    });
+
+    it('is true when the file has at least 1 parallel line but no inline lines for any reason', () => {
+      const noInlineLines = getDiffFile({ highlighted_diff_lines: undefined });
+      const emptyInlineLines = getDiffFile({ highlighted_diff_lines: [] });
+
+      expect(diffsHelper.isSingleViewStyle(noInlineLines)).toBeTruthy();
+      expect(diffsHelper.isSingleViewStyle(emptyInlineLines)).toBeTruthy();
+    });
+
+    it('is true when the file does not have any inline lines or parallel lines for any reason', () => {
+      const noLines = getDiffFile({
+        highlighted_diff_lines: undefined,
+        parallel_diff_lines: undefined,
+      });
+      const emptyLines = getDiffFile({
+        highlighted_diff_lines: [],
+        parallel_diff_lines: [],
+      });
+
+      expect(diffsHelper.isSingleViewStyle(noLines)).toBeTruthy();
+      expect(diffsHelper.isSingleViewStyle(emptyLines)).toBeTruthy();
+      expect(diffsHelper.isSingleViewStyle()).toBeTruthy();
+    });
+
+    it('is false when the file has both inline and parallel lines', () => {
+      expect(diffsHelper.isSingleViewStyle(getDiffFile())).toBeFalsy();
+    });
+  });
+
+  describe.each`
+    context                                     | inline       | parallel     | blob                         | expected
+    ${'only has inline lines'}                  | ${['line']}  | ${undefined} | ${undefined}                 | ${true}
+    ${'only has parallel lines'}                | ${undefined} | ${['line']}  | ${undefined}                 | ${true}
+    ${"doesn't have inline, parallel, or blob"} | ${undefined} | ${undefined} | ${undefined}                 | ${true}
+    ${'has blob readable text'}                 | ${undefined} | ${undefined} | ${{ readable_text: 'text' }} | ${false}
+  `('when hasDiff', ({ context, inline, parallel, blob, expected }) => {
+    it(`${context}`, () => {
+      const diffFile = getDiffFile({
+        highlighted_diff_lines: inline,
+        parallel_diff_lines: parallel,
+        blob,
+      });
+
+      expect(diffsHelper.hasDiff(diffFile)).toEqual(expected);
+    });
+  });
+});
--- a/spec/frontend/monitoring/components/dashboard_spec.js
+++ b/spec/frontend/monitoring/components/dashboard_spec.js
@ -345,7 +345,7 @@ describe('Dashboard', () => {

        it('metrics can be swapped', done => {
          const firstDraggable = findDraggables().at(0);
-          const mockMetrics = [...metricsGroupsAPIResponse[1].panels];
+          const mockMetrics = [...metricsGroupsAPIResponse.panel_groups[1].panels];

          const firstTitle = mockMetrics[0].title;
          const secondTitle = mockMetrics[1].title;
--- a/spec/frontend/monitoring/mock_data.js
+++ b/spec/frontend/monitoring/mock_data.js
@ -331,77 +331,80 @@ export const mockedQueryResultPayloadCoresTotal = {
  ],
 };

-export const metricsGroupsAPIResponse = [
-  {
-    group: 'Response metrics (NGINX Ingress VTS)',
-    priority: 10,
-    panels: [
-      {
-        metrics: [
-          {
-            id: 'response_metrics_nginx_ingress_throughput_status_code',
-            label: 'Status Code',
-            metric_id: 1,
-            prometheus_endpoint_path:
-              '/root/autodevops-deploy/environments/32/prometheus/api/v1/query_range?query=sum%28rate%28nginx_upstream_responses_total%7Bupstream%3D~%22%25%7Bkube_namespace%7D-%25%7Bci_environment_slug%7D-.%2A%22%7D%5B2m%5D%29%29+by+%28status_code%29',
-            query_range:
-              'sum(rate(nginx_upstream_responses_total{upstream=~"%{kube_namespace}-%{ci_environment_slug}-.*"}[2m])) by (status_code)',
-            unit: 'req / sec',
-          },
-        ],
-        title: 'Throughput',
-        type: 'area-chart',
-        weight: 1,
-        y_label: 'Requests / Sec',
-      },
-    ],
-  },
-  {
-    group: 'System metrics (Kubernetes)',
-    priority: 5,
-    panels: [
-      {
-        title: 'Memory Usage (Pod average)',
-        type: 'area-chart',
-        y_label: 'Memory Used per Pod',
-        weight: 2,
-        metrics: [
-          {
-            id: 'system_metrics_kubernetes_container_memory_average',
-            query_range:
-              'avg(sum(container_memory_usage_bytes{container_name!="POD",pod_name=~"^%{ci_environment_slug}-([^c].*|c([^a]|a([^n]|n([^a]|a([^r]|r[^y])))).*|)-(.*)",namespace="%{kube_namespace}"}) by (job)) without (job) / count(avg(container_memory_usage_bytes{container_name!="POD",pod_name=~"^%{ci_environment_slug}-([^c].*|c([^a]|a([^n]|n([^a]|a([^r]|r[^y])))).*|)-(.*)",namespace="%{kube_namespace}"}) without (job)) /1024/1024',
-            label: 'Pod average',
-            unit: 'MB',
-            metric_id: 17,
-            prometheus_endpoint_path:
-              '/root/autodevops-deploy/environments/32/prometheus/api/v1/query_range?query=avg%28sum%28container_memory_usage_bytes%7Bcontainer_name%21%3D%22POD%22%2Cpod_name%3D~%22%5E%25%7Bci_environment_slug%7D-%28%5B%5Ec%5D.%2A%7Cc%28%5B%5Ea%5D%7Ca%28%5B%5En%5D%7Cn%28%5B%5Ea%5D%7Ca%28%5B%5Er%5D%7Cr%5B%5Ey%5D%29%29%29%29.%2A%7C%29-%28.%2A%29%22%2Cnamespace%3D%22%25%7Bkube_namespace%7D%22%7D%29+by+%28job%29%29+without+%28job%29+%2F+count%28avg%28container_memory_usage_bytes%7Bcontainer_name%21%3D%22POD%22%2Cpod_name%3D~%22%5E%25%7Bci_environment_slug%7D-%28%5B%5Ec%5D.%2A%7Cc%28%5B%5Ea%5D%7Ca%28%5B%5En%5D%7Cn%28%5B%5Ea%5D%7Ca%28%5B%5Er%5D%7Cr%5B%5Ey%5D%29%29%29%29.%2A%7C%29-%28.%2A%29%22%2Cnamespace%3D%22%25%7Bkube_namespace%7D%22%7D%29+without+%28job%29%29+%2F1024%2F1024',
-            appearance: {
-              line: {
-                width: 2,
+export const metricsGroupsAPIResponse = {
+  dashboard: 'Environment metrics',
+  panel_groups: [
+    {
+      group: 'Response metrics (NGINX Ingress VTS)',
+      priority: 10,
+      panels: [
+        {
+          metrics: [
+            {
+              id: 'response_metrics_nginx_ingress_throughput_status_code',
+              label: 'Status Code',
+              metric_id: 1,
+              prometheus_endpoint_path:
+                '/root/autodevops-deploy/environments/32/prometheus/api/v1/query_range?query=sum%28rate%28nginx_upstream_responses_total%7Bupstream%3D~%22%25%7Bkube_namespace%7D-%25%7Bci_environment_slug%7D-.%2A%22%7D%5B2m%5D%29%29+by+%28status_code%29',
+              query_range:
+                'sum(rate(nginx_upstream_responses_total{upstream=~"%{kube_namespace}-%{ci_environment_slug}-.*"}[2m])) by (status_code)',
+              unit: 'req / sec',
+            },
+          ],
+          title: 'Throughput',
+          type: 'area-chart',
+          weight: 1,
+          y_label: 'Requests / Sec',
+        },
+      ],
+    },
+    {
+      group: 'System metrics (Kubernetes)',
+      priority: 5,
+      panels: [
+        {
+          title: 'Memory Usage (Pod average)',
+          type: 'area-chart',
+          y_label: 'Memory Used per Pod',
+          weight: 2,
+          metrics: [
+            {
+              id: 'system_metrics_kubernetes_container_memory_average',
+              query_range:
+                'avg(sum(container_memory_usage_bytes{container_name!="POD",pod_name=~"^%{ci_environment_slug}-([^c].*|c([^a]|a([^n]|n([^a]|a([^r]|r[^y])))).*|)-(.*)",namespace="%{kube_namespace}"}) by (job)) without (job) / count(avg(container_memory_usage_bytes{container_name!="POD",pod_name=~"^%{ci_environment_slug}-([^c].*|c([^a]|a([^n]|n([^a]|a([^r]|r[^y])))).*|)-(.*)",namespace="%{kube_namespace}"}) without (job)) /1024/1024',
+              label: 'Pod average',
+              unit: 'MB',
+              metric_id: 17,
+              prometheus_endpoint_path:
+                '/root/autodevops-deploy/environments/32/prometheus/api/v1/query_range?query=avg%28sum%28container_memory_usage_bytes%7Bcontainer_name%21%3D%22POD%22%2Cpod_name%3D~%22%5E%25%7Bci_environment_slug%7D-%28%5B%5Ec%5D.%2A%7Cc%28%5B%5Ea%5D%7Ca%28%5B%5En%5D%7Cn%28%5B%5Ea%5D%7Ca%28%5B%5Er%5D%7Cr%5B%5Ey%5D%29%29%29%29.%2A%7C%29-%28.%2A%29%22%2Cnamespace%3D%22%25%7Bkube_namespace%7D%22%7D%29+by+%28job%29%29+without+%28job%29+%2F+count%28avg%28container_memory_usage_bytes%7Bcontainer_name%21%3D%22POD%22%2Cpod_name%3D~%22%5E%25%7Bci_environment_slug%7D-%28%5B%5Ec%5D.%2A%7Cc%28%5B%5Ea%5D%7Ca%28%5B%5En%5D%7Cn%28%5B%5Ea%5D%7Ca%28%5B%5Er%5D%7Cr%5B%5Ey%5D%29%29%29%29.%2A%7C%29-%28.%2A%29%22%2Cnamespace%3D%22%25%7Bkube_namespace%7D%22%7D%29+without+%28job%29%29+%2F1024%2F1024',
+              appearance: {
+                line: {
+                  width: 2,
+                },
              },
            },
-          },
-        ],
-      },
-      {
-        title: 'Core Usage (Total)',
-        type: 'area-chart',
-        y_label: 'Total Cores',
-        weight: 3,
-        metrics: [
-          {
-            id: 'system_metrics_kubernetes_container_cores_total',
-            query_range:
-              'avg(sum(rate(container_cpu_usage_seconds_total{container_name!="POD",pod_name=~"^%{ci_environment_slug}-(.*)",namespace="%{kube_namespace}"}[15m])) by (job)) without (job)',
-            label: 'Total',
-            unit: 'cores',
-            metric_id: 13,
-          },
-        ],
-      },
-    ],
-  },
-];
+          ],
+        },
+        {
+          title: 'Core Usage (Total)',
+          type: 'area-chart',
+          y_label: 'Total Cores',
+          weight: 3,
+          metrics: [
+            {
+              id: 'system_metrics_kubernetes_container_cores_total',
+              query_range:
+                'avg(sum(rate(container_cpu_usage_seconds_total{container_name!="POD",pod_name=~"^%{ci_environment_slug}-(.*)",namespace="%{kube_namespace}"}[15m])) by (job)) without (job)',
+              label: 'Total',
+              unit: 'cores',
+              metric_id: 13,
+            },
+          ],
+        },
+      ],
+    },
+  ],
+};

 export const environmentData = [
  {
--- a/spec/frontend/monitoring/store/actions_spec.js
+++ b/spec/frontend/monitoring/store/actions_spec.js
@ -298,7 +298,7 @@ describe('Monitoring store actions', () => {
      );
      expect(commit).toHaveBeenCalledWith(
        types.RECEIVE_METRICS_DATA_SUCCESS,
-        metricsDashboardResponse.dashboard.panel_groups,
+        metricsDashboardResponse.dashboard,
      );
      expect(dispatch).toHaveBeenCalledWith('fetchPrometheusMetrics', params);
    });
@ -441,7 +441,7 @@ describe('Monitoring store actions', () => {
    beforeEach(() => {
      state = storeState();
      [metric] = metricsDashboardResponse.dashboard.panel_groups[0].panels[0].metrics;
-      [data] = metricsGroupsAPIResponse[0].panels[0].metrics;
+      [data] = metricsGroupsAPIResponse.panel_groups[0].panels[0].metrics;
    });

    it('commits result', done => {
--- a/spec/frontend/monitoring/store/mutations_spec.js
+++ b/spec/frontend/monitoring/store/mutations_spec.js
@ -100,12 +100,12 @@ describe('Monitoring mutations', () => {
        values: [[0, 1], [1, 1], [1, 3]],
      },
    ];
-    const dashboardGroups = metricsDashboardResponse.dashboard.panel_groups;
+    const { dashboard } = metricsDashboardResponse;
    const getMetric = () => stateCopy.dashboard.panel_groups[0].panels[0].metrics[0];

    describe('REQUEST_METRIC_RESULT', () => {
      beforeEach(() => {
-        mutations[types.RECEIVE_METRICS_DATA_SUCCESS](stateCopy, dashboardGroups);
+        mutations[types.RECEIVE_METRICS_DATA_SUCCESS](stateCopy, dashboard);
      });
      it('stores a loading state on a metric', () => {
        expect(stateCopy.showEmptyState).toBe(true);
@ -128,7 +128,7 @@ describe('Monitoring mutations', () => {

    describe('RECEIVE_METRIC_RESULT_SUCCESS', () => {
      beforeEach(() => {
-        mutations[types.RECEIVE_METRICS_DATA_SUCCESS](stateCopy, dashboardGroups);
+        mutations[types.RECEIVE_METRICS_DATA_SUCCESS](stateCopy, dashboard);
      });
      it('clears empty state', () => {
        expect(stateCopy.showEmptyState).toBe(true);
@ -161,7 +161,7 @@ describe('Monitoring mutations', () => {

    describe('RECEIVE_METRIC_RESULT_FAILURE', () => {
      beforeEach(() => {
-        mutations[types.RECEIVE_METRICS_DATA_SUCCESS](stateCopy, dashboardGroups);
+        mutations[types.RECEIVE_METRICS_DATA_SUCCESS](stateCopy, dashboard);
      });
      it('maintains the loading state when a metric fails', () => {
        expect(stateCopy.showEmptyState).toBe(true);
--- a/spec/helpers/projects/error_tracking_helper_spec.rb
+++ b/spec/helpers/projects/error_tracking_helper_spec.rb
@ -80,11 +80,20 @@ describe Projects::ErrorTrackingHelper do
    let(:issue_id) { 1234 }
    let(:route_params) { [project.owner, project, issue_id, { format: :json }] }
    let(:details_path) { details_namespace_project_error_tracking_index_path(*route_params) }
+    let(:project_path) { project.full_path }
    let(:stack_trace_path) { stack_trace_namespace_project_error_tracking_index_path(*route_params) }
    let(:issues_path) { project_issues_path(project) }

    let(:result) { helper.error_details_data(project, issue_id) }

+    it 'returns the correct issue id' do
+      expect(result['issue-id']).to eq issue_id
+    end
+
+    it 'returns the correct project path' do
+      expect(result['project-path']).to eq project_path
+    end
+
    it 'returns the correct details path' do
      expect(result['issue-details-path']).to eq details_path
    end
--- a/spec/javascripts/diffs/components/app_spec.js
+++ b/spec/javascripts/diffs/components/app_spec.js
@ -10,6 +10,7 @@ import CompareVersions from '~/diffs/components/compare_versions.vue';
 import HiddenFilesWarning from '~/diffs/components/hidden_files_warning.vue';
 import CommitWidget from '~/diffs/components/commit_widget.vue';
 import TreeList from '~/diffs/components/tree_list.vue';
+import { INLINE_DIFF_VIEW_TYPE, PARALLEL_DIFF_VIEW_TYPE } from '~/diffs/constants';
 import createDiffsStore from '../create_diffs_store';
 import diffsMockData from '../mock_data/merge_request_diffs';

@ -41,7 +42,6 @@ describe('diffs/components/app', () => {
        changesEmptyStateIllustration: '',
        dismissEndpoint: '',
        showSuggestPopover: true,
-        useSingleDiffStyle: false,
        ...props,
      },
      store,
@ -53,6 +53,12 @@ describe('diffs/components/app', () => {
    });
  }

+  function getOppositeViewType(currentViewType) {
+    return currentViewType === INLINE_DIFF_VIEW_TYPE
+      ? PARALLEL_DIFF_VIEW_TYPE
+      : INLINE_DIFF_VIEW_TYPE;
+  }
+
  beforeEach(() => {
    // setup globals (needed for component to mount :/)
    window.mrTabs = jasmine.createSpyObj('mrTabs', ['resetViewContainer']);
@ -82,9 +88,146 @@ describe('diffs/components/app', () => {
      spyOn(wrapper.vm, 'startRenderDiffsQueue');
      spyOn(wrapper.vm, 'unwatchDiscussions');
      store.state.diffs.retrievingBatches = true;
+      store.state.diffs.diffFiles = [];
      wrapper.vm.$nextTick(done);
    });

+    describe('when the diff view type changes and it should load a single diff view style', () => {
+      const noLinesDiff = {
+        highlighted_diff_lines: [],
+        parallel_diff_lines: [],
+      };
+      const parallelLinesDiff = {
+        highlighted_diff_lines: [],
+        parallel_diff_lines: ['line'],
+      };
+      const inlineLinesDiff = {
+        highlighted_diff_lines: ['line'],
+        parallel_diff_lines: [],
+      };
+      const fullDiff = {
+        highlighted_diff_lines: ['line'],
+        parallel_diff_lines: ['line'],
+      };
+
+      function expectFetchToOccur({
+        vueInstance,
+        done = () => {},
+        batch = false,
+        existingFiles = 1,
+      } = {}) {
+        vueInstance.$nextTick(() => {
+          expect(vueInstance.diffFiles.length).toEqual(existingFiles);
+
+          if (!batch) {
+            expect(vueInstance.fetchDiffFiles).toHaveBeenCalled();
+            expect(vueInstance.fetchDiffFilesBatch).not.toHaveBeenCalled();
+          } else {
+            expect(vueInstance.fetchDiffFiles).not.toHaveBeenCalled();
+            expect(vueInstance.fetchDiffFilesBatch).toHaveBeenCalled();
+          }
+
+          done();
+        });
+      }
+
+      beforeEach(() => {
+        wrapper.vm.glFeatures.singleMrDiffView = true;
+      });
+
+      it('fetches diffs if it has none', done => {
+        wrapper.vm.isLatestVersion = () => false;
+
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: false, existingFiles: 0, done });
+      });
+
+      it('fetches diffs if it has both view styles, but no lines in either', done => {
+        wrapper.vm.isLatestVersion = () => false;
+
+        store.state.diffs.diffFiles.push(noLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, done });
+      });
+
+      it('fetches diffs if it only has inline view style', done => {
+        wrapper.vm.isLatestVersion = () => false;
+
+        store.state.diffs.diffFiles.push(inlineLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, done });
+      });
+
+      it('fetches diffs if it only has parallel view style', done => {
+        wrapper.vm.isLatestVersion = () => false;
+
+        store.state.diffs.diffFiles.push(parallelLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, done });
+      });
+
+      it('fetches batch diffs if it has none', done => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, existingFiles: 0, done });
+      });
+
+      it('fetches batch diffs if it has both view styles, but no lines in either', done => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffFiles.push(noLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, done });
+      });
+
+      it('fetches batch diffs if it only has inline view style', done => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffFiles.push(inlineLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, done });
+      });
+
+      it('fetches batch diffs if it only has parallel view style', done => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffFiles.push(parallelLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, done });
+      });
+
+      it('does not fetch diffs if it has already fetched both styles of diff', () => {
+        wrapper.vm.glFeatures.diffsBatchLoad = false;
+
+        store.state.diffs.diffFiles.push(fullDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expect(wrapper.vm.diffFiles.length).toEqual(1);
+        expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
+      });
+
+      it('does not fetch batch diffs if it has already fetched both styles of diff', () => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffFiles.push(fullDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expect(wrapper.vm.diffFiles.length).toEqual(1);
+        expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
+      });
+    });
+
    it('calls fetchDiffFiles if diffsBatchLoad is not enabled', done => {
      wrapper.vm.glFeatures.diffsBatchLoad = false;
      wrapper.vm.fetchData(false);
--- a/spec/javascripts/diffs/store/actions_spec.js
+++ b/spec/javascripts/diffs/store/actions_spec.js
@ -120,7 +120,7 @@ describe('DiffsStoreActions', () => {

  describe('fetchDiffFiles', () => {
    it('should fetch diff files', done => {
-      const endpoint = '/fetch/diff/files?w=1';
+      const endpoint = '/fetch/diff/files?view=inline&w=1';
      const mock = new MockAdapter(axios);
      const res = { diff_files: 1, merge_request_diffs: [] };
      mock.onGet(endpoint).reply(200, res);
@ -128,7 +128,7 @@ describe('DiffsStoreActions', () => {
      testAction(
        fetchDiffFiles,
        {},
-        { endpoint },
+        { endpoint, diffFiles: [], showWhitespace: false, diffViewType: 'inline' },
        [
          { type: types.SET_LOADING, payload: true },
          { type: types.SET_LOADING, payload: false },
--- a/spec/javascripts/diffs/store/mutations_spec.js
+++ b/spec/javascripts/diffs/store/mutations_spec.js
@ -52,7 +52,14 @@ describe('DiffsStoreMutations', () => {

  describe('SET_DIFF_DATA', () => {
    it('should set diff data type properly', () => {
-      const state = {};
+      const state = {
+        diffFiles: [
+          {
+            content_sha: diffFileMockData.content_sha,
+            file_hash: diffFileMockData.file_hash,
+          },
+        ],
+      };
      const diffMock = {
        diff_files: [diffFileMockData],
      };
@ -62,9 +69,41 @@ describe('DiffsStoreMutations', () => {
      const firstLine = state.diffFiles[0].parallel_diff_lines[0];

      expect(firstLine.right.text).toBeUndefined();
+      expect(state.diffFiles.length).toEqual(1);
      expect(state.diffFiles[0].renderIt).toEqual(true);
      expect(state.diffFiles[0].collapsed).toEqual(false);
    });
+
+    describe('given diffsBatchLoad feature flag is enabled', () => {
+      beforeEach(() => {
+        gon.features = { diffsBatchLoad: true };
+      });
+
+      afterEach(() => {
+        delete gon.features;
+      });
+
+      it('should not modify the existing state', () => {
+        const state = {
+          diffFiles: [
+            {
+              content_sha: diffFileMockData.content_sha,
+              file_hash: diffFileMockData.file_hash,
+              highlighted_diff_lines: [],
+            },
+          ],
+        };
+        const diffMock = {
+          diff_files: [diffFileMockData],
+        };
+
+        mutations[types.SET_DIFF_DATA](state, diffMock);
+
+        // If the batch load is enabled, there shouldn't be any processing
+        // done on the existing state object, so we shouldn't have this.
+        expect(state.diffFiles[0].parallel_diff_lines).toBeUndefined();
+      });
+    });
  });

  describe('SET_DIFFSET_DIFF_DATA_BATCH_DATA', () => {
@ -168,11 +207,17 @@ describe('DiffsStoreMutations', () => {
    it('should update the state with the given data for the given file hash', () => {
      const fileHash = 123;
      const state = {
-        diffFiles: [{}, { file_hash: fileHash, existing_field: 0 }],
+        diffFiles: [{}, { content_sha: 'abc', file_hash: fileHash, existing_field: 0 }],
      };
      const data = {
        diff_files: [
-          { file_hash: fileHash, extra_field: 1, existing_field: 1, viewer: { name: 'text' } },
+          {
+            content_sha: 'abc',
+            file_hash: fileHash,
+            extra_field: 1,
+            existing_field: 1,
+            viewer: { name: 'text' },
+          },
        ],
      };

@ -208,7 +253,7 @@ describe('DiffsStoreMutations', () => {
                  discussions: [],
                },
                right: {
-                  line_code: 'ABC_1',
+                  line_code: 'ABC_2',
                  discussions: [],
                },
              },
@ -274,7 +319,7 @@ describe('DiffsStoreMutations', () => {
                  discussions: [],
                },
                right: {
-                  line_code: 'ABC_1',
+                  line_code: 'ABC_2',
                  discussions: [],
                },
              },
@ -352,7 +397,7 @@ describe('DiffsStoreMutations', () => {
                  discussions: [],
                },
                right: {
-                  line_code: 'ABC_1',
+                  line_code: 'ABC_2',
                  discussions: [],
                },
              },
@ -448,6 +493,7 @@ describe('DiffsStoreMutations', () => {
                discussions: [],
              },
            ],
+            parallel_diff_lines: [],
          },
        ],
      };
--- a/spec/javascripts/diffs/store/utils_spec.js
+++ b/spec/javascripts/diffs/store/utils_spec.js
@ -314,11 +314,29 @@ describe('DiffsStoreUtils', () => {
  });

  describe('prepareDiffData', () => {
+    let mock;
    let preparedDiff;
+    let splitInlineDiff;
+    let splitParallelDiff;
+    let completedDiff;

    beforeEach(() => {
-      preparedDiff = { diff_files: [getDiffFileMock()] };
+      mock = getDiffFileMock();
+      preparedDiff = { diff_files: [mock] };
+      splitInlineDiff = {
+        diff_files: [Object.assign({}, mock, { parallel_diff_lines: undefined })],
+      };
+      splitParallelDiff = {
+        diff_files: [Object.assign({}, mock, { highlighted_diff_lines: undefined })],
+      };
+      completedDiff = {
+        diff_files: [Object.assign({}, mock, { highlighted_diff_lines: undefined })],
+      };
+
      utils.prepareDiffData(preparedDiff);
+      utils.prepareDiffData(splitInlineDiff);
+      utils.prepareDiffData(splitParallelDiff);
+      utils.prepareDiffData(completedDiff, [mock]);
    });

    it('sets the renderIt and collapsed attribute on files', () => {
@ -359,6 +377,19 @@ describe('DiffsStoreUtils', () => {

      expect(firstLine.line_code).toEqual(firstLine.right.line_code);
    });
+
+    it('guarantees an empty array for both diff styles', () => {
+      expect(splitInlineDiff.diff_files[0].parallel_diff_lines.length).toEqual(0);
+      expect(splitInlineDiff.diff_files[0].highlighted_diff_lines.length).toBeGreaterThan(0);
+      expect(splitParallelDiff.diff_files[0].parallel_diff_lines.length).toBeGreaterThan(0);
+      expect(splitParallelDiff.diff_files[0].highlighted_diff_lines.length).toEqual(0);
+    });
+
+    it('merges existing diff files with newly loaded diff files to ensure split diffs are eventually completed', () => {
+      expect(completedDiff.diff_files.length).toEqual(1);
+      expect(completedDiff.diff_files[0].parallel_diff_lines.length).toBeGreaterThan(0);
+      expect(completedDiff.diff_files[0].highlighted_diff_lines.length).toBeGreaterThan(0);
+    });
  });

  describe('isDiscussionApplicableToLine', () => {
--- a/spec/lib/gitlab/background_migration/activate_prometheus_services_for_shared_cluster_applications_spec.rb
+++ b/spec/lib/gitlab/background_migration/activate_prometheus_services_for_shared_cluster_applications_spec.rb
@ -1,75 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe Gitlab::BackgroundMigration::ActivatePrometheusServicesForSharedClusterApplications, :migration, schema: 2019_12_20_102807 do
-  include MigrationHelpers::PrometheusServiceHelpers
-
-  let(:namespaces) { table(:namespaces) }
-  let(:projects) { table(:projects) }
-  let(:services) { table(:services) }
-  let(:namespace) { namespaces.create(name: 'user', path: 'user') }
-  let(:project) { projects.create(namespace_id: namespace.id) }
-
-  let(:columns) do
-    %w(project_id active properties type template push_events
-       issues_events merge_requests_events tag_push_events
-       note_events category default wiki_page_events pipeline_events
-       confidential_issues_events commit_events job_events
-       confidential_note_events deployment_events)
-  end
-
-  describe '#perform' do
-    it 'is idempotent' do
-      expect { subject.perform(project.id) }.to change { services.order(:id).map { |row| row.attributes } }
-
-      expect { subject.perform(project.id) }.not_to change { services.order(:id).map { |row| row.attributes } }
-    end
-
-    context 'non prometheus services' do
-      it 'does not change them' do
-        other_type = 'SomeOtherService'
-        services.create(service_params_for(project.id, active: true, type: other_type))
-
-        expect { subject.perform(project.id) }.not_to change { services.where(type: other_type).order(:id).map { |row| row.attributes } }
-      end
-    end
-
-    context 'prometheus services are configured manually ' do
-      it 'does not change them' do
-        properties = '{"api_url":"http://test.dev","manual_configuration":"1"}'
-        services.create(service_params_for(project.id, properties: properties, active: false))
-
-        expect { subject.perform(project.id) }.not_to change { services.order(:id).map { |row| row.attributes } }
-      end
-    end
-
-    context 'prometheus integration services do not exist' do
-      it 'creates missing services entries' do
-        subject.perform(project.id)
-
-        rows = services.order(:id).map { |row| row.attributes.slice(*columns).symbolize_keys }
-
-        expect([service_params_for(project.id, active: true)]).to eq rows
-      end
-    end
-
-    context 'prometheus integration services exist' do
-      context 'in active state' do
-        it 'does not change them' do
-          services.create(service_params_for(project.id, active: true))
-
-          expect { subject.perform(project.id) }.not_to change { services.order(:id).map { |row| row.attributes } }
-        end
-      end
-
-      context 'not in active state' do
-        it 'sets active attribute to true' do
-          service = services.create(service_params_for(project.id))
-
-          expect { subject.perform(project.id) }.to change { service.reload.active? }.from(false).to(true)
-        end
-      end
-    end
-  end
-end
--- a/spec/lib/gitlab/ci/pipeline/chain/validate/abilities_spec.rb
+++ b/spec/lib/gitlab/ci/pipeline/chain/validate/abilities_spec.rb
@ -76,45 +76,8 @@ describe Gitlab::Ci::Pipeline::Chain::Validate::Abilities do
    end
  end

-  context 'when pipeline triggered by legacy trigger' do
-    let(:user) { nil }
-    let(:trigger_request) do
-      build_stubbed(:ci_trigger_request, trigger: build_stubbed(:ci_trigger, owner: nil))
-    end
-
-    context 'when :use_legacy_pipeline_triggers feature flag is enabled' do
-      before do
-        stub_feature_flags(use_legacy_pipeline_triggers: true)
-        step.perform!
-      end
-
-      it 'allows legacy triggers to create a pipeline' do
-        expect(pipeline).to be_valid
-      end
-
-      it 'does not break the chain' do
-        expect(step.break?).to eq false
-      end
-    end
-
-    context 'when :use_legacy_pipeline_triggers feature flag is disabled' do
-      before do
-        stub_feature_flags(use_legacy_pipeline_triggers: false)
-        step.perform!
-      end
-
-      it 'prevents legacy triggers from creating a pipeline' do
-        expect(pipeline.errors.to_a).to include /Trigger token is invalid/
-      end
-
-      it 'breaks the pipeline builder chain' do
-        expect(step.break?).to eq true
-      end
-    end
-  end
-
-  describe '#allowed_to_create?' do
-    subject { step.allowed_to_create? }
+  describe '#allowed_to_write_ref?' do
+    subject { step.send(:allowed_to_write_ref?) }

    context 'when user is a developer' do
      before do
--- a/spec/lib/gitlab/import_export/all_models.yml
+++ b/spec/lib/gitlab/import_export/all_models.yml
@ -578,3 +578,30 @@ zoom_meetings:
 sentry_issue:
 - issue
 design_versions: *version
+epic:
+- subscriptions
+- award_emoji
+- description_versions
+- author
+- assignee
+- issues
+- epic_issues
+- milestone
+- notes
+- label_links
+- labels
+- todos
+- metrics
+- group
+- parent
+- children
+- updated_by
+- last_edited_by
+- closed_by
+- start_date_sourcing_milestone
+- due_date_sourcing_milestone
+- start_date_sourcing_epic
+- due_date_sourcing_epic
+- events
+- resource_label_events
+- user_mentions
--- a/spec/lib/gitlab/import_export/project_tree_restorer_spec.rb
+++ b/spec/lib/gitlab/import_export/project_tree_restorer_spec.rb
@ -36,10 +36,6 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
    end

    context 'JSON' do
-      before do
-        stub_feature_flags(use_legacy_pipeline_triggers: false)
-      end
-
      it 'restores models based on JSON' do
        expect(@restored_project_json).to be_truthy
      end
@ -502,7 +498,7 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
      end

      it_behaves_like 'restores project successfully',
-                      issues: 2,
+                      issues: 3,
                      labels: 2,
                      label_with_priorities: 'A project label',
                      milestones: 2,
@ -515,7 +511,7 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do

      it 'restores issue states' do
        expect(project.issues.with_state(:closed).count).to eq(1)
-        expect(project.issues.with_state(:opened).count).to eq(1)
+        expect(project.issues.with_state(:opened).count).to eq(2)
      end
    end

--- a/spec/lib/gitlab/import_export/safe_model_attributes.yml
+++ b/spec/lib/gitlab/import_export/safe_model_attributes.yml
@ -766,3 +766,33 @@ ContainerExpirationPolicy:
 - older_than
 - keep_n
 - enabled
+Epic:
+  - id
+  - milestone_id
+  - group_id
+  - author_id
+  - assignee_id
+  - iid
+  - updated_by_id
+  - last_edited_by_id
+  - lock_version
+  - start_date
+  - end_date
+  - last_edited_at
+  - created_at
+  - updated_at
+  - title
+  - description
+  - start_date_sourcing_milestone_id
+  - due_date_sourcing_milestone_id
+  - start_date_fixed
+  - due_date_fixed
+  - start_date_is_fixed
+  - due_date_is_fixed
+  - closed_by_id
+  - closed_at
+  - parent_id
+  - relative_position
+  - state_id
+  - start_date_sourcing_epic_id
+  - due_date_sourcing_epic_id
--- a/spec/migrations/20191204114127_delete_legacy_triggers_spec.rb
+++ b/spec/migrations/20191204114127_delete_legacy_triggers_spec.rb
@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20191204114127_delete_legacy_triggers.rb')
+
+describe DeleteLegacyTriggers, :migration, schema: 2019_11_25_140458 do
+  let(:ci_trigger_table) { table(:ci_triggers) }
+  let(:user) { table(:users).create!(name: 'test', email: 'test@example.com', projects_limit: 1) }
+
+  before do
+    @trigger_with_user = ci_trigger_table.create!(owner_id: user.id)
+    ci_trigger_table.create!(owner_id: nil)
+    ci_trigger_table.create!(owner_id: nil)
+  end
+
+  it 'removes legacy triggers which has null owner_id' do
+    expect do
+      migrate!
+    end.to change(ci_trigger_table, :count).by(-2)
+
+    expect(ci_trigger_table.all).to eq([@trigger_with_user])
+  end
+end
--- a/spec/migrations/patch_prometheus_services_for_shared_cluster_applications_spec.rb
+++ b/spec/migrations/patch_prometheus_services_for_shared_cluster_applications_spec.rb
@ -1,134 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-require Rails.root.join('db', 'post_migrate', '20191220102807_patch_prometheus_services_for_shared_cluster_applications.rb')
-
-describe PatchPrometheusServicesForSharedClusterApplications, :migration, :sidekiq do
-  include MigrationHelpers::PrometheusServiceHelpers
-
-  let(:namespaces) { table(:namespaces) }
-  let(:projects) { table(:projects) }
-  let(:services) { table(:services) }
-  let(:clusters) { table(:clusters) }
-  let(:cluster_groups) { table(:cluster_groups) }
-  let(:clusters_applications_prometheus) { table(:clusters_applications_prometheus) }
-  let(:namespace) { namespaces.create!(name: 'gitlab', path: 'gitlab-org') }
-
-  let(:application_statuses) do
-    {
-      errored: -1,
-      installed: 3,
-      updated: 5
-    }
-  end
-
-  let(:cluster_types) do
-    {
-      instance_type: 1,
-      group_type: 2
-    }
-  end
-
-  describe '#up' do
-    let!(:project_with_missing_service) { projects.create!(name: 'gitlab', path: 'gitlab-ce', namespace_id: namespace.id) }
-    let(:project_with_inactive_service) { projects.create!(name: 'gitlab', path: 'gitlab-ee', namespace_id: namespace.id) }
-    let(:project_with_active_service) { projects.create!(name: 'gitlab', path: 'gitlab-ee', namespace_id: namespace.id) }
-    let(:project_with_manual_active_service) { projects.create!(name: 'gitlab', path: 'gitlab-ee', namespace_id: namespace.id) }
-    let(:project_with_manual_inactive_service) { projects.create!(name: 'gitlab', path: 'gitlab-ee', namespace_id: namespace.id) }
-    let(:project_with_active_not_prometheus_service) { projects.create!(name: 'gitlab', path: 'gitlab-ee', namespace_id: namespace.id) }
-    let(:project_with_inactive_not_prometheus_service) { projects.create!(name: 'gitlab', path: 'gitlab-ee', namespace_id: namespace.id) }
-
-    before do
-      services.create(service_params_for(project_with_inactive_service.id, active: false))
-      services.create(service_params_for(project_with_active_service.id, active: true))
-      services.create(service_params_for(project_with_active_not_prometheus_service.id, active: true, type: 'other'))
-      services.create(service_params_for(project_with_inactive_not_prometheus_service.id, active: false, type: 'other'))
-      services.create(service_params_for(project_with_manual_inactive_service.id, active: false, properties: { some: 'data' }.to_json))
-      services.create(service_params_for(project_with_manual_active_service.id, active: true, properties: { some: 'data' }.to_json))
-    end
-
-    shared_examples 'patch prometheus services post migration' do
-      context 'prometheus application is installed on the cluster' do
-        it 'schedules a background migration' do
-          clusters_applications_prometheus.create(cluster_id: cluster.id, status: application_statuses[:installed], version: '123')
-
-          Sidekiq::Testing.fake! do
-            Timecop.freeze do
-              background_migrations = [["ActivatePrometheusServicesForSharedClusterApplications", project_with_missing_service.id],
-                                       ["ActivatePrometheusServicesForSharedClusterApplications", project_with_inactive_service.id],
-                                       ["ActivatePrometheusServicesForSharedClusterApplications", project_with_active_not_prometheus_service.id],
-                                       ["ActivatePrometheusServicesForSharedClusterApplications", project_with_inactive_not_prometheus_service.id]]
-
-              migrate!
-
-              enqueued_migrations = BackgroundMigrationWorker.jobs.map { |job| job['args'] }
-              expect(enqueued_migrations).to match_array(background_migrations)
-            end
-          end
-        end
-      end
-
-      context 'prometheus application was recently updated on the cluster' do
-        it 'schedules a background migration' do
-          clusters_applications_prometheus.create(cluster_id: cluster.id, status: application_statuses[:updated], version: '123')
-
-          Sidekiq::Testing.fake! do
-            Timecop.freeze do
-              background_migrations = [["ActivatePrometheusServicesForSharedClusterApplications", project_with_missing_service.id],
-                                       ["ActivatePrometheusServicesForSharedClusterApplications", project_with_inactive_service.id],
-                                       ["ActivatePrometheusServicesForSharedClusterApplications", project_with_active_not_prometheus_service.id],
-                                       ["ActivatePrometheusServicesForSharedClusterApplications", project_with_inactive_not_prometheus_service.id]]
-
-              migrate!
-
-              enqueued_migrations = BackgroundMigrationWorker.jobs.map { |job| job['args'] }
-              expect(enqueued_migrations).to match_array(background_migrations)
-            end
-          end
-        end
-      end
-
-      context 'prometheus application failed to install on the cluster' do
-        it 'does not schedule a background migration' do
-          clusters_applications_prometheus.create(cluster_id: cluster.id, status: application_statuses[:errored], version: '123')
-
-          Sidekiq::Testing.fake! do
-            Timecop.freeze do
-              migrate!
-
-              expect(BackgroundMigrationWorker.jobs.size).to eq 0
-            end
-          end
-        end
-      end
-
-      context 'prometheus application is NOT installed on the cluster' do
-        it 'does not schedule a background migration' do
-          Sidekiq::Testing.fake! do
-            Timecop.freeze do
-              migrate!
-
-              expect(BackgroundMigrationWorker.jobs.size).to eq 0
-            end
-          end
-        end
-      end
-    end
-
-    context 'Cluster is group_type' do
-      let(:cluster) { clusters.create(name: 'cluster', cluster_type: cluster_types[:group_type]) }
-
-      before do
-        cluster_groups.create(group_id: namespace.id, cluster_id: cluster.id)
-      end
-
-      it_behaves_like 'patch prometheus services post migration'
-    end
-
-    context 'Cluster is instance_type' do
-      let(:cluster) { clusters.create(name: 'cluster', cluster_type: cluster_types[:instance_type]) }
-
-      it_behaves_like 'patch prometheus services post migration'
-    end
-  end
-end
--- a/spec/models/ci/trigger_spec.rb
+++ b/spec/models/ci/trigger_spec.rb
@ -11,6 +11,10 @@ describe Ci::Trigger do
    it { is_expected.to have_many(:trigger_requests) }
  end

+  describe 'validations' do
+    it { is_expected.to validate_presence_of(:owner) }
+  end
+
  describe 'before_validation' do
    it 'sets an random token if none provided' do
      trigger = create(:ci_trigger_without_token, project: project)
@ -35,63 +39,22 @@ describe Ci::Trigger do
    end
  end

-  describe '#legacy?' do
-    let(:trigger) { create(:ci_trigger, owner: owner, project: project) }
-
-    subject { trigger }
-
-    context 'when owner is blank' do
-      let(:owner) { nil }
-
-      it { is_expected.to be_legacy }
-    end
-
-    context 'when owner is set' do
-      let(:owner) { create(:user) }
-
-      it { is_expected.not_to be_legacy }
-    end
-  end
-
  describe '#can_access_project?' do
    let(:owner) { create(:user) }
    let(:trigger) { create(:ci_trigger, owner: owner, project: project) }

-    context 'when owner is blank' do
+    subject { trigger.can_access_project? }
+
+    context 'and is member of the project' do
      before do
-        stub_feature_flags(use_legacy_pipeline_triggers: false)
-        trigger.update_attribute(:owner, nil)
+        project.add_developer(owner)
      end

-      subject { trigger.can_access_project? }
-
-      it { is_expected.to eq(false) }
-
-      context 'when :use_legacy_pipeline_triggers feature flag is enabled' do
-        before do
-          stub_feature_flags(use_legacy_pipeline_triggers: true)
-        end
-
-        subject { trigger.can_access_project? }
-
-        it { is_expected.to eq(true) }
-      end
+      it { is_expected.to eq(true) }
    end

-    context 'when owner is set' do
-      subject { trigger.can_access_project? }
-
-      context 'and is member of the project' do
-        before do
-          project.add_developer(owner)
-        end
-
-        it { is_expected.to eq(true) }
-      end
-
-      context 'and is not member of the project' do
-        it { is_expected.to eq(false) }
-      end
+    context 'and is not member of the project' do
+      it { is_expected.to eq(false) }
    end
  end
 end
--- a/spec/policies/ci/trigger_policy_spec.rb
+++ b/spec/policies/ci/trigger_policy_spec.rb
@ -10,60 +10,6 @@ describe Ci::TriggerPolicy do
  subject { described_class.new(user, trigger) }

  describe '#rules' do
-    context 'when owner is undefined' do
-      before do
-        stub_feature_flags(use_legacy_pipeline_triggers: false)
-        trigger.update_attribute(:owner, nil)
-      end
-
-      context 'when user is maintainer of the project' do
-        before do
-          project.add_maintainer(user)
-        end
-
-        it { is_expected.to be_allowed(:manage_trigger) }
-        it { is_expected.not_to be_allowed(:admin_trigger) }
-      end
-
-      context 'when user is developer of the project' do
-        before do
-          project.add_developer(user)
-        end
-
-        it { is_expected.not_to be_allowed(:manage_trigger) }
-        it { is_expected.not_to be_allowed(:admin_trigger) }
-      end
-
-      context 'when :use_legacy_pipeline_triggers feature flag is enabled' do
-        before do
-          stub_feature_flags(use_legacy_pipeline_triggers: true)
-        end
-
-        context 'when user is maintainer of the project' do
-          before do
-            project.add_maintainer(user)
-          end
-
-          it { is_expected.to be_allowed(:manage_trigger) }
-          it { is_expected.to be_allowed(:admin_trigger) }
-        end
-
-        context 'when user is developer of the project' do
-          before do
-            project.add_developer(user)
-          end
-
-          it { is_expected.not_to be_allowed(:manage_trigger) }
-          it { is_expected.not_to be_allowed(:admin_trigger) }
-        end
-
-        context 'when user is not member of the project' do
-          it { is_expected.not_to be_allowed(:manage_trigger) }
-          it { is_expected.not_to be_allowed(:admin_trigger) }
-        end
-      end
-    end
-
    context 'when owner is an user' do
      before do
        trigger.update!(owner: user)
--- a/spec/requests/api/triggers_spec.rb
+++ b/spec/requests/api/triggers_spec.rb
@ -87,22 +87,6 @@ describe API::Triggers do
          expect(pipeline.variables.map { |v| { v.key => v.value } }.last).to eq(variables)
        end
      end
-
-      context 'when legacy trigger' do
-        before do
-          trigger.update(owner: nil)
-        end
-
-        it 'creates pipeline' do
-          post api("/projects/#{project.id}/trigger/pipeline"), params: options.merge(ref: 'master')
-
-          expect(response).to have_gitlab_http_status(201)
-          expect(json_response).to include('id' => pipeline.id)
-          pipeline.builds.reload
-          expect(pipeline.builds.pending.size).to eq(2)
-          expect(pipeline.builds.size).to eq(5)
-        end
-      end
    end

    context 'when triggering a pipeline from a trigger token' do
--- a/spec/routing/admin_routing_spec.rb
+++ b/spec/routing/admin_routing_spec.rb
@ -161,3 +161,17 @@ describe Admin::GroupsController, "routing" do
    expect(get("/admin/groups/#{name}/edit")).to route_to('admin/groups#edit', id: name)
  end
 end
+
+describe Admin::SessionsController, "routing" do
+  it "to #new" do
+    expect(get("/admin/session/new")).to route_to('admin/sessions#new')
+  end
+
+  it "to #create" do
+    expect(post("/admin/session")).to route_to('admin/sessions#create')
+  end
+
+  it "to #destroy" do
+    expect(post("/admin/session/destroy")).to route_to('admin/sessions#destroy')
+  end
+end
--- a/spec/routing/routing_spec.rb
+++ b/spec/routing/routing_spec.rb
@ -256,10 +256,8 @@ describe "Authentication", "routing" do
    expect(post("/users/sign_in")).to route_to('sessions#create')
  end

-  # sign_out with GET instead of DELETE facilitates ad-hoc single-sign-out processes
-  # (https://gitlab.com/gitlab-org/gitlab-foss/issues/39708)
-  it "GET /users/sign_out" do
-    expect(get("/users/sign_out")).to route_to('sessions#destroy')
+  it "POST /users/sign_out" do
+    expect(post("/users/sign_out")).to route_to('sessions#destroy')
  end

  it "POST /users/password" do
--- a/spec/services/ci/create_pipeline_service_spec.rb
+++ b/spec/services/ci/create_pipeline_service_spec.rb
@ -1123,21 +1123,6 @@ describe Ci::CreatePipelineService do
      it_behaves_like 'when ref is protected'
    end

-    context 'when ref is not protected' do
-      context 'when trigger belongs to no one' do
-        let(:user) {}
-        let(:trigger) { create(:ci_trigger, owner: nil) }
-        let(:trigger_request) { create(:ci_trigger_request, trigger: trigger) }
-        let(:pipeline) { execute_service(trigger_request: trigger_request) }
-
-        it 'creates an unprotected pipeline' do
-          expect(pipeline).to be_persisted
-          expect(pipeline).not_to be_protected
-          expect(Ci::Pipeline.count).to eq(1)
-        end
-      end
-    end
-
    context 'when pipeline is running for a tag' do
      before do
        config = YAML.dump(test: { script: 'test', only: ['branches'] },
--- a/spec/support/migrations_helpers/prometheus_service_helpers.rb
+++ b/spec/support/migrations_helpers/prometheus_service_helpers.rb
@ -1,35 +0,0 @@
-# frozen_string_literal: true
-
-module MigrationHelpers
-  module PrometheusServiceHelpers
-    def service_params_for(project_id, params = {})
-      {
-        project_id: project_id,
-        active: false,
-        properties: '{}',
-        type: 'PrometheusService',
-        template: false,
-        push_events: true,
-        issues_events: true,
-        merge_requests_events: true,
-        tag_push_events: true,
-        note_events: true,
-        category: 'monitoring',
-        default: false,
-        wiki_page_events: true,
-        pipeline_events: true,
-        confidential_issues_events: true,
-        commit_events: true,
-        job_events: true,
-        confidential_note_events: true,
-        deployment_events: false
-      }.merge(params)
-    end
-
-    def row_attributes(entity)
-      entity.attributes.with_indifferent_access.tap do |hash|
-        hash.merge!(hash.slice(:created_at, :updated_at).transform_values { |v| v.to_s(:db) })
-      end
-    end
-  end
-end
--- a/spec/support/shared_examples/merge_requests_rendering_a_single_diff_version.rb
+++ b/spec/support/shared_examples/merge_requests_rendering_a_single_diff_version.rb
@ -1,21 +0,0 @@
-# frozen_string_literal: true
-
-# This pending test can be removed when `single_mr_diff_view` is enabled by default
-# disabling the feature flag above is then not needed anymore.
-RSpec.shared_examples 'rendering a single diff version' do |attribute|
-  before do
-    stub_feature_flags(diffs_batch_load: false)
-  end
-
-  pending 'allows editing diff settings single_mr_diff_view is enabled' do
-    project = create(:project, :repository)
-    user = project.creator
-    merge_request = create(:merge_request, source_project: project)
-    stub_feature_flags(single_mr_diff_view: true)
-    sign_in(user)
-
-    visit(diffs_project_merge_request_path(project, merge_request))
-
-    expect(page).to have_selector('.js-show-diff-settings')
-  end
-end
--- a/yarn.lock
+++ b/yarn.lock
@ -5640,6 +5640,11 @@ immediate@~3.0.5:
  resolved "https://registry.yarnpkg.com/immediate/-/immediate-3.0.6.tgz#9db1dbd0faf8de6fbe0f5dd5e56bb606280de69b"
  integrity sha1-nbHb0Pr43m++D13V5Wu2BigN5ps=

+immer@^5.2.1:
+  version "5.2.1"
+  resolved "https://registry.yarnpkg.com/immer/-/immer-5.2.1.tgz#7d4f74c242178e87151d595f48db1b5c51580485"
+  integrity sha512-9U1GEbJuH6nVoyuFRgTQDGMzcBuNBPfXM3M7Pp/sdmYKTKYOBUZGgeUb9H57GfLK/xC1DMLarWX2FrhMBfUJ8g==
+
 import-fresh@^2.0.0:
  version "2.0.0"
  resolved "https://registry.yarnpkg.com/import-fresh/-/import-fresh-2.0.0.tgz#d81355c15612d386c61f9ddd3922d4304822a546"