diff --git a/.vale.ini b/.vale.ini
index 89a669ec7ff..13b198b9148 100644
--- a/.vale.ini
+++ b/.vale.ini
@@ -1,40 +1,9 @@
-# Vale configuration file, taken from https://errata-ai.github.io/vale/config/
+# Vale configuration file.
+#
+# For more information, see https://errata-ai.gitbook.io/vale/getting-started/configuration.
 
-# The relative path to the folder containing linting rules (styles)
-# -----------------------------------------------------------------
-StylesPath = doc/.linting/vale/styles
-
-# Minimum alert level
-# -------------------
-# The minimum alert level to display (suggestion, warning, or error).
-# If integrated into CI, builds fail by default on error-level alerts,
-# unless you execute Vale with the --no-exit flag
+StylesPath = doc/.vale
 MinAlertLevel = suggestion
 
-# Should Vale parse any file formats other than .md files as Markdown?
-# --------------------------------------------------------------------
-[formats]
-mdx = md
-
-# What file types should Vale test?
-# ----------------------------------
 [*.md]
-
-# Styles to load
-# --------------
-# What styles, located in the StylesPath folder, should Vale load?
-# Vale also currently includes write-good, proselint, joblint, and vale
 BasedOnStyles = gitlab
-
-# Enabling or disabling specific rules in a style
-# -----------------------------------------------
-# To disable a rule in an enabled style, use the following format:
-# {style}.{filename} = NO
-# To enable a single rule in a disabled style, use the following format:
-# vale.Editorializing = YES
-
-# Altering the severity of a rule in a style
-# ------------------------------------------
-# To change the reporting level (suggestion, warning, error) of a rule,
-# use the following format: {style}.{filename} = {level}
-# vale.Hedging = error
diff --git a/app/assets/javascripts/api.js b/app/assets/javascripts/api.js
index dc6ea148047..022d79ecf49 100644
--- a/app/assets/javascripts/api.js
+++ b/app/assets/javascripts/api.js
@@ -1,5 +1,3 @@
-import $ from 'jquery';
-import _ from 'underscore';
 import axios from './lib/utils/axios_utils';
 import { joinPaths } from './lib/utils/url_utility';
 import flash from '~/flash';
@@ -70,7 +68,7 @@ const Api = {
   },
 
   // Return groups list. Filtered by query
-  groups(query, options, callback = $.noop) {
+  groups(query, options, callback = () => {}) {
     const url = Api.buildUrl(Api.groupsPath);
     return axios
       .get(url, {
@@ -108,7 +106,7 @@ const Api = {
   },
 
   // Return projects list. Filtered by query
-  projects(query, options, callback = _.noop) {
+  projects(query, options, callback = () => {}) {
     const url = Api.buildUrl(Api.projectsPath);
     const defaults = {
       search: query,
diff --git a/app/assets/javascripts/environments/components/enable_review_app_button.vue b/app/assets/javascripts/environments/components/enable_review_app_button.vue
index 2f9e9cb628f..8fbbc5189bf 100644
--- a/app/assets/javascripts/environments/components/enable_review_app_button.vue
+++ b/app/assets/javascripts/environments/components/enable_review_app_button.vue
@@ -26,15 +26,17 @@ export default {
   modalInfo: {
     closeText: s__('EnableReviewApp|Close'),
     copyToClipboardText: s__('EnableReviewApp|Copy snippet text'),
-    copyString: `deploy_review
+    copyString: `deploy_review:
   stage: deploy
   script:
     - echo "Deploy a review app"
   environment:
     name: review/$CI_COMMIT_REF_NAME
     url: https://$CI_ENVIRONMENT_SLUG.example.com
-  only: branches
-  except: master`,
+  only:
+    - branches
+  except:
+    - master`,
     id: 'enable-review-app-info',
     title: s__('ReviewApp|Enable Review App'),
   },
diff --git a/app/assets/javascripts/ide/components/commit_sidebar/list.vue b/app/assets/javascripts/ide/components/commit_sidebar/list.vue
index 2e273d45506..a15e22d4742 100644
--- a/app/assets/javascripts/ide/components/commit_sidebar/list.vue
+++ b/app/assets/javascripts/ide/components/commit_sidebar/list.vue
@@ -94,7 +94,7 @@ export default {
             data-boundary="viewport"
             @click="openDiscardModal"
           >
-            <icon :size="16" name="remove-all" class="ml-auto mr-auto" />
+            <icon :size="16" name="remove-all" class="ml-auto mr-auto position-top-0" />
           </button>
         </div>
       </div>
diff --git a/app/assets/javascripts/ide/components/pipelines/list.vue b/app/assets/javascripts/ide/components/pipelines/list.vue
index b61d0a47795..3a63fc32639 100644
--- a/app/assets/javascripts/ide/components/pipelines/list.vue
+++ b/app/assets/javascripts/ide/components/pipelines/list.vue
@@ -59,7 +59,7 @@ export default {
     <gl-loading-icon v-if="showLoadingIcon" :size="2" class="prepend-top-default" />
     <template v-else-if="hasLoadedPipeline">
       <header v-if="latestPipeline" class="ide-tree-header ide-pipeline-header">
-        <ci-icon :status="latestPipeline.details.status" :size="24" />
+        <ci-icon :status="latestPipeline.details.status" :size="24" class="d-flex" />
         <span class="prepend-left-8">
           <strong> {{ __('Pipeline') }} </strong>
           <a
@@ -76,6 +76,7 @@ export default {
         :help-page-path="links.ciHelpPagePath"
         :empty-state-svg-path="pipelinesEmptyStateSvgPath"
         :can-set-ci="true"
+        class="mb-auto mt-auto"
       />
       <div v-else-if="latestPipeline.yamlError" class="bs-callout bs-callout-danger">
         <p class="append-bottom-0">{{ __('Found errors in your .gitlab-ci.yml:') }}</p>
diff --git a/app/assets/javascripts/lib/utils/icon_utils.js b/app/assets/javascripts/lib/utils/icon_utils.js
index 7b8dd9bbef7..97ee773358d 100644
--- a/app/assets/javascripts/lib/utils/icon_utils.js
+++ b/app/assets/javascripts/lib/utils/icon_utils.js
@@ -1,18 +1,40 @@
-/* eslint-disable import/prefer-default-export */
-
+import { memoize } from 'lodash';
 import axios from '~/lib/utils/axios_utils';
 
 /**
- * Retrieve SVG icon path content from gitlab/svg sprite icons
- * @param {String} name
+ * Resolves to a DOM that contains GitLab icons
+ * in svg format. Memoized to avoid duplicate requests
  */
-export const getSvgIconPathContent = name =>
+const getSvgDom = memoize(() =>
   axios
     .get(gon.sprite_icons)
-    .then(({ data: svgs }) =>
-      new DOMParser()
-        .parseFromString(svgs, 'text/xml')
-        .querySelector(`#${name} path`)
-        .getAttribute('d'),
-    )
+    .then(({ data: svgs }) => new DOMParser().parseFromString(svgs, 'text/xml'))
+    .catch(() => {
+      getSvgDom.cache.clear();
+    }),
+);
+
+/**
+ * Clears the memoized SVG content.
+ *
+ * You probably don't need to invoke this function unless
+ * sprite_icons are updated.
+ */
+export const clearSvgIconPathContentCache = () => {
+  getSvgDom.cache.clear();
+};
+
+/**
+ * Retrieve SVG icon path content from gitlab/svg sprite icons.
+ *
+ * Content loaded is cached.
+ *
+ * @param {String} name - Icon name
+ * @returns A promise that resolves to the svg path
+ */
+export const getSvgIconPathContent = name =>
+  getSvgDom()
+    .then(doc => {
+      return doc.querySelector(`#${name} path`).getAttribute('d');
+    })
     .catch(() => null);
diff --git a/app/assets/stylesheets/page_bundles/_ide_monaco_overrides.scss b/app/assets/stylesheets/page_bundles/_ide_monaco_overrides.scss
new file mode 100644
index 00000000000..c47901dc177
--- /dev/null
+++ b/app/assets/stylesheets/page_bundles/_ide_monaco_overrides.scss
@@ -0,0 +1,146 @@
+
+// stylelint-disable selector-class-pattern
+// stylelint-disable selector-max-compound-selectors
+// stylelint-disable stylelint-gitlab/duplicate-selectors
+// stylelint-disable stylelint-gitlab/utility-classes
+
+.blob-editor-container {
+  flex: 1;
+  height: 0;
+  display: flex;
+  flex-direction: column;
+  justify-content: center;
+
+  .vertical-center {
+    min-height: auto;
+  }
+
+  .monaco-editor .lines-content .cigr {
+    display: none;
+  }
+
+  .monaco-editor .selected-text {
+    z-index: 1;
+  }
+
+  .monaco-editor .view-lines {
+    z-index: 2;
+  }
+
+  .is-readonly,
+  .editor.original {
+    .view-lines {
+      cursor: default;
+    }
+
+    .cursors-layer {
+      display: none;
+    }
+  }
+
+  .is-deleted {
+    .editor.modified {
+      .margin-view-overlays,
+      .lines-content,
+      .decorationsOverviewRuler {
+        // !important to override monaco inline styles
+        display: none !important;
+      }
+    }
+
+    .diffOverviewRuler.modified {
+      // !important to override monaco inline styles
+      display: none !important;
+    }
+  }
+
+  .is-added {
+    .editor.original {
+      .margin-view-overlays,
+      .lines-content,
+      .decorationsOverviewRuler {
+        // !important to override monaco inline styles
+        display: none !important;
+      }
+    }
+
+    .diffOverviewRuler.original {
+      // !important to override monaco inline styles
+      display: none !important;
+    }
+  }
+
+  .monaco-diff-editor.vs {
+    .editor.modified {
+      box-shadow: none;
+    }
+
+    .diagonal-fill {
+      display: none !important;
+    }
+
+    .diffOverview {
+      background-color: $white-light;
+      border-left: 1px solid $white-dark;
+      cursor: ns-resize;
+    }
+
+    .diffViewport {
+      display: none;
+    }
+
+    .char-insert {
+      background-color: $line-added-dark;
+    }
+
+    .char-delete {
+      background-color: $line-removed-dark;
+    }
+
+    .line-numbers {
+      color: $black-transparent;
+    }
+
+    .view-overlays {
+      .line-insert {
+        background-color: $line-added;
+      }
+
+      .line-delete {
+        background-color: $line-removed;
+      }
+    }
+
+    .margin {
+      background-color: $white-light;
+      border-right: 1px solid $gray-100;
+
+      .line-insert {
+        border-right: 1px solid $line-added-dark;
+      }
+
+      .line-delete {
+        border-right: 1px solid $line-removed-dark;
+      }
+    }
+
+    .margin-view-overlays .insert-sign,
+    .margin-view-overlays .delete-sign {
+      opacity: 0.4;
+    }
+  }
+}
+
+.multi-file-editor-holder {
+  height: 100%;
+  min-height: 0; // firefox fix
+
+  &.is-readonly .vs,
+  .vs .editor.original {
+    .monaco-editor,
+    .monaco-editor-background,
+    .monaco-editor .inputarea.ime-input {
+      background-color: $gray-50;
+    }
+  }
+}
diff --git a/app/assets/stylesheets/page_bundles/ide.scss b/app/assets/stylesheets/page_bundles/ide.scss
index a748c669ee8..c37f75d1533 100644
--- a/app/assets/stylesheets/page_bundles/ide.scss
+++ b/app/assets/stylesheets/page_bundles/ide.scss
@@ -1,6 +1,7 @@
 @import 'framework/variables';
 @import 'framework/mixins';
 @import './ide_mixins';
+@import './ide_monaco_overrides';
 
 $search-list-icon-width: 18px;
 $ide-activity-bar-width: 60px;
@@ -16,11 +17,6 @@ $ide-commit-header-height: 48px;
   display: inline-block;
 }
 
-.fade-enter,
-.fade-leave-to {
-  opacity: 0;
-}
-
 .commit-message {
   @include str-truncated(250px);
 }
@@ -49,10 +45,6 @@ $ide-commit-header-height: 48px;
   flex-direction: column;
   flex: 1;
   min-height: 0; // firefox fix
-
-  a {
-    color: $gl-text-color;
-  }
 }
 
 .multi-file-loading-container {
@@ -160,157 +152,6 @@ $ide-commit-header-height: 48px;
   height: 0;
 }
 
-// stylelint-disable selector-class-pattern
-// stylelint-disable selector-max-compound-selectors
-// stylelint-disable stylelint-gitlab/duplicate-selectors
-// stylelint-disable stylelint-gitlab/utility-classes
-
-.blob-editor-container {
-  flex: 1;
-  height: 0;
-  display: flex;
-  flex-direction: column;
-  justify-content: center;
-
-  .vertical-center {
-    min-height: auto;
-  }
-
-  .monaco-editor .lines-content .cigr {
-    display: none;
-  }
-
-  .monaco-editor .selected-text {
-    z-index: 1;
-  }
-
-  .monaco-editor .view-lines {
-    z-index: 2;
-  }
-
-  .is-readonly,
-  .editor.original {
-    .view-lines {
-      cursor: default;
-    }
-
-    .cursors-layer {
-      display: none;
-    }
-  }
-
-  .is-deleted {
-    .editor.modified {
-      .margin-view-overlays,
-      .lines-content,
-      .decorationsOverviewRuler {
-        // !important to override monaco inline styles
-        display: none !important;
-      }
-    }
-
-    .diffOverviewRuler.modified {
-      // !important to override monaco inline styles
-      display: none !important;
-    }
-  }
-
-  .is-added {
-    .editor.original {
-      .margin-view-overlays,
-      .lines-content,
-      .decorationsOverviewRuler {
-        // !important to override monaco inline styles
-        display: none !important;
-      }
-    }
-
-    .diffOverviewRuler.original {
-      // !important to override monaco inline styles
-      display: none !important;
-    }
-  }
-
-  .monaco-diff-editor.vs {
-    .editor.modified {
-      box-shadow: none;
-    }
-
-    .diagonal-fill {
-      display: none !important;
-    }
-
-    .diffOverview {
-      background-color: $white-light;
-      border-left: 1px solid $white-dark;
-      cursor: ns-resize;
-    }
-
-    .diffViewport {
-      display: none;
-    }
-
-    .char-insert {
-      background-color: $line-added-dark;
-    }
-
-    .char-delete {
-      background-color: $line-removed-dark;
-    }
-
-    .line-numbers {
-      color: $black-transparent;
-    }
-
-    .view-overlays {
-      .line-insert {
-        background-color: $line-added;
-      }
-
-      .line-delete {
-        background-color: $line-removed;
-      }
-    }
-
-    .margin {
-      background-color: $white-light;
-      border-right: 1px solid $gray-100;
-
-      .line-insert {
-        border-right: 1px solid $line-added-dark;
-      }
-
-      .line-delete {
-        border-right: 1px solid $line-removed-dark;
-      }
-    }
-
-    .margin-view-overlays .insert-sign,
-    .margin-view-overlays .delete-sign {
-      opacity: 0.4;
-    }
-  }
-}
-
-.multi-file-editor-holder {
-  height: 100%;
-  min-height: 0; // firefox fix
-
-  &.is-readonly .vs,
-  .vs .editor.original {
-    .monaco-editor,
-    .monaco-editor-background,
-    .monaco-editor .inputarea.ime-input {
-      background-color: $gray-50;
-    }
-  }
-}
-
-// stylelint-enable selector-class-pattern
-// stylelint-enable selector-max-compound-selectors
-// stylelint-enable stylelint-gitlab/duplicate-selectors
-// stylelint-enable stylelint-gitlab/utility-classes
-
 .preview-container {
   flex-grow: 1;
   position: relative;
@@ -671,10 +512,6 @@ $ide-commit-header-height: 48px;
   width: $ide-commit-row-height;
   height: $ide-commit-row-height;
   color: inherit;
-
-  > svg {
-    top: 0;
-  }
 }
 
 .ide-commit-file-count {
@@ -864,39 +701,39 @@ $ide-commit-header-height: 48px;
     margin-left: auto;
   }
 
-  .ide-nav-dropdown {
-    width: 100%;
-    margin-bottom: 12px;
+  button {
+    color: $gl-text-color;
+  }
+}
 
-    .dropdown-menu {
-      width: 385px;
-      max-height: initial;
-    }
+.ide-nav-dropdown {
+  width: 100%;
+  margin-bottom: 12px;
 
-    .dropdown-menu-toggle {
-      svg {
-        vertical-align: middle;
-        color: $gray-700;
+  .dropdown-menu {
+    width: 385px;
+    max-height: initial;
+  }
 
-        &:hover {
-          color: $gray-700;
-        }
-      }
+  .dropdown-menu-toggle {
+    svg {
+      vertical-align: middle;
+      color: $gray-700;
 
       &:hover {
-        background-color: $white-normal;
+        color: $gray-700;
       }
     }
 
-    &.show {
-      .dropdown-menu-toggle {
-        background-color: $white-dark;
-      }
+    &:hover {
+      background-color: $white-normal;
     }
   }
 
-  button {
-    color: $gl-text-color;
+  &.show {
+    .dropdown-menu-toggle {
+      background-color: $white-dark;
+    }
   }
 }
 
@@ -945,6 +782,8 @@ $ide-commit-header-height: 48px;
   transform: translateY(0);
 }
 
+.fade-enter,
+.fade-leave-to,
 .commit-form-slide-up-enter,
 .commit-form-slide-up-leave-to {
   opacity: 0;
@@ -1063,9 +902,6 @@ $ide-commit-header-height: 48px;
   @include ide-trace-view();
 
   .empty-state {
-    margin-top: auto;
-    margin-bottom: auto;
-
     p {
       margin: $grid-size 0;
       text-align: center;
@@ -1092,10 +928,6 @@ $ide-commit-header-height: 48px;
   min-height: 55px;
   padding-left: $gl-padding;
   padding-right: $gl-padding;
-
-  .ci-status-icon {
-    display: flex;
-  }
 }
 
 .ide-job-item {
@@ -1135,7 +967,7 @@ $ide-commit-header-height: 48px;
 }
 
 .ide-nav-form {
-  .nav-links li {
+  li {
     width: 50%;
     padding-left: 0;
     padding-right: 0;
@@ -1222,10 +1054,6 @@ $ide-commit-header-height: 48px;
     background-color: $blue-500;
     outline: 0;
   }
-
-  svg {
-    fill: currentColor;
-  }
 }
 
 .ide-new-btn {
diff --git a/app/services/system_note_service.rb b/app/services/system_note_service.rb
index 8a0f44b4e93..1b9f5971f73 100644
--- a/app/services/system_note_service.rb
+++ b/app/services/system_note_service.rb
@@ -241,6 +241,10 @@ module SystemNoteService
   def zoom_link_removed(issue, project, author)
     ::SystemNotes::ZoomService.new(noteable: issue, project: project, author: author).zoom_link_removed
   end
+
+  def auto_resolve_prometheus_alert(noteable, project, author)
+    ::SystemNotes::IssuablesService.new(noteable: noteable, project: project, author: author).auto_resolve_prometheus_alert
+  end
 end
 
 SystemNoteService.prepend_if_ee('EE::SystemNoteService')
diff --git a/app/services/system_notes/issuables_service.rb b/app/services/system_notes/issuables_service.rb
index b555760f88e..275c64bea89 100644
--- a/app/services/system_notes/issuables_service.rb
+++ b/app/services/system_notes/issuables_service.rb
@@ -288,6 +288,12 @@ module SystemNotes
       create_note(NoteSummary.new(noteable, project, author, body, action: 'closed'))
     end
 
+    def auto_resolve_prometheus_alert
+      body = 'automatically closed this issue because the alert resolved.'
+
+      create_note(NoteSummary.new(noteable, project, author, body, action: 'closed'))
+    end
+
     private
 
     def cross_reference_note_content(gfm_reference)
diff --git a/changelogs/unreleased/stop_environments.yml b/changelogs/unreleased/stop_environments.yml
new file mode 100644
index 00000000000..ea92be202af
--- /dev/null
+++ b/changelogs/unreleased/stop_environments.yml
@@ -0,0 +1,5 @@
+---
+title: 'Fixes stop_review job upon expired artifacts from previous stages'
+merge_request: 27258
+author: Jack Lei
+type: fixed
diff --git a/doc/.linting/vale/styles/gitlab/Contractions.yml b/doc/.vale/gitlab/Contractions.yml
similarity index 100%
rename from doc/.linting/vale/styles/gitlab/Contractions.yml
rename to doc/.vale/gitlab/Contractions.yml
diff --git a/doc/.linting/vale/styles/gitlab/FirstPerson.yml b/doc/.vale/gitlab/FirstPerson.yml
similarity index 100%
rename from doc/.linting/vale/styles/gitlab/FirstPerson.yml
rename to doc/.vale/gitlab/FirstPerson.yml
diff --git a/doc/.linting/vale/styles/gitlab/InternalLinkExtension.yml b/doc/.vale/gitlab/InternalLinkExtension.yml
similarity index 100%
rename from doc/.linting/vale/styles/gitlab/InternalLinkExtension.yml
rename to doc/.vale/gitlab/InternalLinkExtension.yml
diff --git a/doc/.linting/vale/styles/gitlab/LatinTerms.yml b/doc/.vale/gitlab/LatinTerms.yml
similarity index 100%
rename from doc/.linting/vale/styles/gitlab/LatinTerms.yml
rename to doc/.vale/gitlab/LatinTerms.yml
diff --git a/doc/.linting/vale/styles/gitlab/OxfordComma.yml b/doc/.vale/gitlab/OxfordComma.yml
similarity index 100%
rename from doc/.linting/vale/styles/gitlab/OxfordComma.yml
rename to doc/.vale/gitlab/OxfordComma.yml
diff --git a/doc/.linting/vale/styles/gitlab/RelativeLinks.yml b/doc/.vale/gitlab/RelativeLinks.yml
similarity index 100%
rename from doc/.linting/vale/styles/gitlab/RelativeLinks.yml
rename to doc/.vale/gitlab/RelativeLinks.yml
diff --git a/doc/.linting/vale/styles/gitlab/SentenceSpacing.yml b/doc/.vale/gitlab/SentenceSpacing.yml
similarity index 100%
rename from doc/.linting/vale/styles/gitlab/SentenceSpacing.yml
rename to doc/.vale/gitlab/SentenceSpacing.yml
diff --git a/doc/.linting/vale/styles/gitlab/Substitutions.yml b/doc/.vale/gitlab/Substitutions.yml
similarity index 100%
rename from doc/.linting/vale/styles/gitlab/Substitutions.yml
rename to doc/.vale/gitlab/Substitutions.yml
diff --git a/doc/ci/review_apps/img/enable_review_app_v12_8.png b/doc/ci/review_apps/img/enable_review_app_v12_8.png
index 7d40f49725f..264e4834e72 100644
Binary files a/doc/ci/review_apps/img/enable_review_app_v12_8.png and b/doc/ci/review_apps/img/enable_review_app_v12_8.png differ
diff --git a/doc/development/contributing/issue_workflow.md b/doc/development/contributing/issue_workflow.md
index 4d84e921acf..46d1d4c2414 100644
--- a/doc/development/contributing/issue_workflow.md
+++ b/doc/development/contributing/issue_workflow.md
@@ -81,6 +81,8 @@ already reserved for category labels).
 The descriptions on the [labels page](https://gitlab.com/groups/gitlab-org/-/labels)
 explain what falls under each type label.
 
+The GitLab handbook documents [when something is a bug and when it is a feature request.](https://about.gitlab.com/handbook/product/product-management/process/feature-or-bug.html)
+
 ### Facet labels
 
 Sometimes it's useful to refine the type of an issue. In those cases, you can
diff --git a/doc/development/event_tracking/backend.md b/doc/development/event_tracking/backend.md
new file mode 100644
index 00000000000..dc4d7279671
--- /dev/null
+++ b/doc/development/event_tracking/backend.md
@@ -0,0 +1,5 @@
+---
+redirect_to: '../../telemetry/backend.md'
+---
+
+This document was moved to [another location](../../telemetry/backend.md).
diff --git a/doc/development/event_tracking/frontend.md b/doc/development/event_tracking/frontend.md
new file mode 100644
index 00000000000..0e98daf15bb
--- /dev/null
+++ b/doc/development/event_tracking/frontend.md
@@ -0,0 +1,5 @@
+---
+redirect_to: '../../telemetry/frontend.md'
+---
+
+This document was moved to [another location](../../telemetry/frontend.md).
diff --git a/doc/development/event_tracking/index.md b/doc/development/event_tracking/index.md
new file mode 100644
index 00000000000..ae555e99c6b
--- /dev/null
+++ b/doc/development/event_tracking/index.md
@@ -0,0 +1,5 @@
+---
+redirect_to: '../../telemetry/index.md'
+---
+
+This document was moved to [another location](../../telemetry/index.md).
diff --git a/doc/policy/maintenance.md b/doc/policy/maintenance.md
index 1739c07ccd5..028e372985d 100644
--- a/doc/policy/maintenance.md
+++ b/doc/policy/maintenance.md
@@ -127,7 +127,7 @@ one major version. For example, it is safe to:
   - `9.5.5` -> `9.5.9`
   - `10.6.3` -> `10.6.6`
   - `11.11.1` -> `11.11.8`
-  - `12.0.4` -> `12.0.9`
+  - `12.0.4` -> `12.0.12`
 - Upgrade the minor version:
   - `8.9.4` -> `8.12.3`
   - `9.2.3` -> `9.5.5`
@@ -144,9 +144,10 @@ It's also important to ensure that any background migrations have been fully com
 before upgrading to a new major version. To see the current size of the `background_migration` queue,
 [Check for background migrations before upgrading](../update/README.md#checking-for-background-migrations-before-upgrading).
 
-To ensure background migrations are successful, increment by one minor version during the version jump before installing newer releases.
+From version 12 onwards, an additional step is required. More significant migrations may occur during major release upgrades. To ensure these are successful, increment to the first minor version (`x.0.x`) during the major version jump. Then proceed with upgrading to a newer release.
+
+For example: `11.11.x` -> `12.0.x` -> `12.8.x`
 
-For example: `11.11.x` -> `12.0.x`
 Please see the table below for some examples:
 
 | Latest stable version | Your version | Recommended upgrade path | Note |
@@ -154,7 +155,8 @@ Please see the table below for some examples:
 | 9.4.5                 | 8.13.4       | `8.13.4` -> `8.17.7` -> `9.4.5`                          | `8.17.7` is the last version in version `8` |
 | 10.1.4                | 8.13.4       | `8.13.4 -> 8.17.7 -> 9.5.10 -> 10.1.4`                   | `8.17.7` is the last version in version `8`, `9.5.10` is the last version in version `9` |
 | 11.3.4                | 8.13.4       | `8.13.4` -> `8.17.7` -> `9.5.10` -> `10.8.7` -> `11.3.4` | `8.17.7` is the last version in version `8`, `9.5.10` is the last version in version `9`, `10.8.7` is the last version in version `10` |
-| 12.5.8                | 11.3.4       | `11.3.4` -> `11.11.8` -> `12.0.9` -> `12.5.8`            | `11.11.8` is the last version in version `11` |
+| 12.5.8                | 11.3.4       | `11.3.4` -> `11.11.8` -> `12.0.12` -> `12.5.8`            | `11.11.8` is the last version in version `11`. `12.0.x` [is a required step.](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/23211#note_272842444) |
+| 12.8.5                | 9.2.6       | `9.2.6` -> `9.5.10` -> `10.8.7` -> `11.11.8` -> `12.0.12` -> `12.8.5` | Four intermediate versions required: the final 9.5, 10.8, 11.11 releases, plus 12.0 |
 
 More information about the release procedures can be found in our
 [release documentation](https://gitlab.com/gitlab-org/release/docs). You may also want to read our
diff --git a/lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml b/lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml
index bbfcf53b3d4..c6c8256b4bb 100644
--- a/lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml
+++ b/lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml
@@ -40,6 +40,7 @@ stop_review:
   environment:
     name: review/$CI_COMMIT_REF_NAME
     action: stop
+  dependencies: []
   when: manual
   allow_failure: true
   only:
diff --git a/lib/gitlab/import_export/group/tree_restorer.rb b/lib/gitlab/import_export/group/tree_restorer.rb
index cbaa6929efa..247e39a68b9 100644
--- a/lib/gitlab/import_export/group/tree_restorer.rb
+++ b/lib/gitlab/import_export/group/tree_restorer.rb
@@ -17,9 +17,17 @@ module Gitlab
         end
 
         def restore
-          @tree_hash = @group_hash || read_tree_hash
-          @group_members = @tree_hash.delete('members')
-          @children = @tree_hash.delete('children')
+          @relation_reader ||=
+            if @group_hash.present?
+              ImportExport::JSON::LegacyReader::User.new(@group_hash, reader.group_relation_names)
+            else
+              ImportExport::JSON::LegacyReader::File.new(@path, reader.group_relation_names)
+            end
+
+          @group_members = @relation_reader.consume_relation('members')
+          @children = @relation_reader.consume_attribute('children')
+          @relation_reader.consume_attribute('name')
+          @relation_reader.consume_attribute('path')
 
           if members_mapper.map && restorer.restore
             @children&.each do |group_hash|
@@ -45,21 +53,12 @@ module Gitlab
 
         private
 
-        def read_tree_hash
-          json = IO.read(@path)
-          ActiveSupport::JSON.decode(json)
-        rescue => e
-          @shared.error(e)
-
-          raise Gitlab::ImportExport::Error.new('Incorrect JSON format')
-        end
-
         def restorer
           @relation_tree_restorer ||= RelationTreeRestorer.new(
             user:             @user,
             shared:           @shared,
             importable:       @group,
-            tree_hash:        @tree_hash.except('name', 'path'),
+            relation_reader:  @relation_reader,
             members_mapper:   members_mapper,
             object_builder:   object_builder,
             relation_factory: relation_factory,
diff --git a/lib/gitlab/import_export/json/legacy_reader.rb b/lib/gitlab/import_export/json/legacy_reader.rb
new file mode 100644
index 00000000000..477e41ae3eb
--- /dev/null
+++ b/lib/gitlab/import_export/json/legacy_reader.rb
@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module ImportExport
+    module JSON
+      class LegacyReader
+        class File < LegacyReader
+          def initialize(path, relation_names)
+            @path = path
+            super(relation_names)
+          end
+
+          def valid?
+            ::File.exist?(@path)
+          end
+
+          private
+
+          def tree_hash
+            @tree_hash ||= read_hash
+          end
+
+          def read_hash
+            ActiveSupport::JSON.decode(IO.read(@path))
+          rescue => e
+            Gitlab::ErrorTracking.log_exception(e)
+            raise Gitlab::ImportExport::Error.new('Incorrect JSON format')
+          end
+        end
+
+        class User < LegacyReader
+          def initialize(tree_hash, relation_names)
+            @tree_hash = tree_hash
+            super(relation_names)
+          end
+
+          def valid?
+            @tree_hash.present?
+          end
+
+          protected
+
+          attr_reader :tree_hash
+        end
+
+        def initialize(relation_names)
+          @relation_names = relation_names.map(&:to_s)
+        end
+
+        def valid?
+          raise NotImplementedError
+        end
+
+        def legacy?
+          true
+        end
+
+        def root_attributes(excluded_attributes = [])
+          attributes.except(*excluded_attributes.map(&:to_s))
+        end
+
+        def consume_relation(key)
+          value = relations.delete(key)
+
+          return value unless block_given?
+
+          return if value.nil?
+
+          if value.is_a?(Array)
+            value.each.with_index do |item, idx|
+              yield(item, idx)
+            end
+          else
+            yield(value, 0)
+          end
+        end
+
+        def consume_attribute(key)
+          attributes.delete(key)
+        end
+
+        def sort_ci_pipelines_by_id
+          relations['ci_pipelines']&.sort_by! { |hash| hash['id'] }
+        end
+
+        private
+
+        attr_reader :relation_names
+
+        def tree_hash
+          raise NotImplementedError
+        end
+
+        def attributes
+          @attributes ||= tree_hash.slice!(*relation_names)
+        end
+
+        def relations
+          @relations ||= tree_hash.extract!(*relation_names)
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/import_export/project/tree_loader.rb b/lib/gitlab/import_export/project/tree_loader.rb
deleted file mode 100644
index 6d4737a2d00..00000000000
--- a/lib/gitlab/import_export/project/tree_loader.rb
+++ /dev/null
@@ -1,74 +0,0 @@
-# frozen_string_literal: true
-
-module Gitlab
-  module ImportExport
-    module Project
-      class TreeLoader
-        def load(path, dedup_entries: false)
-          tree_hash = ActiveSupport::JSON.decode(IO.read(path))
-
-          if dedup_entries
-            dedup_tree(tree_hash)
-          else
-            tree_hash
-          end
-        end
-
-        private
-
-        # This function removes duplicate entries from the given tree recursively
-        # by caching nodes it encounters repeatedly. We only consider nodes for
-        # which there can actually be multiple equivalent instances (e.g. strings,
-        # hashes and arrays, but not `nil`s, numbers or booleans.)
-        #
-        # The algorithm uses a recursive depth-first descent with 3 cases, starting
-        # with a root node (the tree/hash itself):
-        # - a node has already been cached; in this case we return it from the cache
-        # - a node has not been cached yet but should be; descend into its children
-        # - a node is neither cached nor qualifies for caching; this is a no-op
-        def dedup_tree(node, nodes_seen = {})
-          if nodes_seen.key?(node) && distinguishable?(node)
-            yield nodes_seen[node]
-          elsif should_dedup?(node)
-            nodes_seen[node] = node
-
-            case node
-            when Array
-              node.each_index do |idx|
-                dedup_tree(node[idx], nodes_seen) do |cached_node|
-                  node[idx] = cached_node
-                end
-              end
-            when Hash
-              node.each do |k, v|
-                dedup_tree(v, nodes_seen) do |cached_node|
-                  node[k] = cached_node
-                end
-              end
-            end
-          else
-            node
-          end
-        end
-
-        # We do not need to consider nodes for which there cannot be multiple instances
-        def should_dedup?(node)
-          node && !(node.is_a?(Numeric) || node.is_a?(TrueClass) || node.is_a?(FalseClass))
-        end
-
-        # We can only safely de-dup values that are distinguishable. True value objects
-        # are always distinguishable by nature. Hashes however can represent entities,
-        # which are identified by ID, not value. We therefore disallow de-duping hashes
-        # that do not have an `id` field, since we might risk dropping entities that
-        # have equal attributes yet different identities.
-        def distinguishable?(node)
-          if node.is_a?(Hash)
-            node.key?('id')
-          else
-            true
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/import_export/project/tree_restorer.rb b/lib/gitlab/import_export/project/tree_restorer.rb
index 295e0d5f348..f8d25e14c02 100644
--- a/lib/gitlab/import_export/project/tree_restorer.rb
+++ b/lib/gitlab/import_export/project/tree_restorer.rb
@@ -4,8 +4,6 @@ module Gitlab
   module ImportExport
     module Project
       class TreeRestorer
-        LARGE_PROJECT_FILE_SIZE_BYTES = 500.megabyte
-
         attr_reader :user
         attr_reader :shared
         attr_reader :project
@@ -14,12 +12,12 @@ module Gitlab
           @user = user
           @shared = shared
           @project = project
-          @tree_loader = TreeLoader.new
         end
 
         def restore
-          @tree_hash = read_tree_hash
-          @project_members = @tree_hash.delete('project_members')
+          @relation_reader = ImportExport::JSON::LegacyReader::File.new(File.join(shared.export_path, 'project.json'), reader.project_relation_names)
+
+          @project_members = @relation_reader.consume_relation('project_members')
 
           if relation_tree_restorer.restore
             import_failure_service.with_retry(action: 'set_latest_merge_request_diff_ids!') do
@@ -37,24 +35,12 @@ module Gitlab
 
         private
 
-        def large_project?(path)
-          File.size(path) >= LARGE_PROJECT_FILE_SIZE_BYTES
-        end
-
-        def read_tree_hash
-          path = File.join(@shared.export_path, 'project.json')
-          @tree_loader.load(path, dedup_entries: large_project?(path))
-        rescue => e
-          Rails.logger.error("Import/Export error: #{e.message}") # rubocop:disable Gitlab/RailsLogger
-          raise Gitlab::ImportExport::Error.new('Incorrect JSON format')
-        end
-
         def relation_tree_restorer
           @relation_tree_restorer ||= RelationTreeRestorer.new(
             user: @user,
             shared: @shared,
             importable: @project,
-            tree_hash: @tree_hash,
+            relation_reader: @relation_reader,
             object_builder: object_builder,
             members_mapper: members_mapper,
             relation_factory: relation_factory,
diff --git a/lib/gitlab/import_export/reader.rb b/lib/gitlab/import_export/reader.rb
index 1390770acef..8d36d05ca6f 100644
--- a/lib/gitlab/import_export/reader.rb
+++ b/lib/gitlab/import_export/reader.rb
@@ -17,10 +17,18 @@ module Gitlab
         tree_by_key(:project)
       end
 
+      def project_relation_names
+        attributes_finder.find_relations_tree(:project).keys
+      end
+
       def group_tree
         tree_by_key(:group)
       end
 
+      def group_relation_names
+        attributes_finder.find_relations_tree(:group).keys
+      end
+
       def group_members_tree
         tree_by_key(:group_members)
       end
diff --git a/lib/gitlab/import_export/relation_tree_restorer.rb b/lib/gitlab/import_export/relation_tree_restorer.rb
index 8359eefc846..466cb03862e 100644
--- a/lib/gitlab/import_export/relation_tree_restorer.rb
+++ b/lib/gitlab/import_export/relation_tree_restorer.rb
@@ -9,13 +9,13 @@ module Gitlab
       attr_reader :user
       attr_reader :shared
       attr_reader :importable
-      attr_reader :tree_hash
+      attr_reader :relation_reader
 
-      def initialize(user:, shared:, importable:, tree_hash:, members_mapper:, object_builder:, relation_factory:, reader:)
+      def initialize(user:, shared:, importable:, relation_reader:, members_mapper:, object_builder:, relation_factory:, reader:)
         @user = user
         @shared = shared
         @importable = importable
-        @tree_hash = tree_hash
+        @relation_reader = relation_reader
         @members_mapper = members_mapper
         @object_builder = object_builder
         @relation_factory = relation_factory
@@ -30,7 +30,7 @@ module Gitlab
             bulk_inserts_enabled = @importable.class == ::Project &&
               Feature.enabled?(:import_bulk_inserts, @importable.group)
             BulkInsertableAssociations.with_bulk_insert(enabled: bulk_inserts_enabled) do
-              update_relation_hashes!
+              fix_ci_pipelines_not_sorted_on_legacy_project_json!
               create_relations!
             end
           end
@@ -57,18 +57,8 @@ module Gitlab
       end
 
       def process_relation!(relation_key, relation_definition)
-        data_hashes = @tree_hash.delete(relation_key)
-        return unless data_hashes
-
-        # we do not care if we process array or hash
-        data_hashes = [data_hashes] unless data_hashes.is_a?(Array)
-
-        relation_index = 0
-
-        # consume and remove objects from memory
-        while data_hash = data_hashes.shift
+        @relation_reader.consume_relation(relation_key) do |data_hash, relation_index|
           process_relation_item!(relation_key, relation_definition, relation_index, data_hash)
-          relation_index += 1
         end
       end
 
@@ -103,10 +93,7 @@ module Gitlab
       end
 
       def update_params!
-        params = @tree_hash.reject do |key, _|
-          relations.include?(key)
-        end
-
+        params = @relation_reader.root_attributes(relations.keys)
         params = params.merge(present_override_params)
 
         # Cleaning all imported and overridden params
@@ -223,8 +210,13 @@ module Gitlab
         }
       end
 
-      def update_relation_hashes!
-        @tree_hash['ci_pipelines']&.sort_by! { |hash| hash['id'] }
+      # Temporary fix for https://gitlab.com/gitlab-org/gitlab/-/issues/27883 when import from legacy project.json
+      # This should be removed once legacy JSON format is deprecated.
+      # Ndjson export file will fix the order during project export.
+      def fix_ci_pipelines_not_sorted_on_legacy_project_json!
+        return unless relation_reader.legacy?
+
+        relation_reader.sort_ci_pipelines_by_id
       end
     end
   end
diff --git a/lib/gitlab/import_export/relation_tree_saver.rb b/lib/gitlab/import_export/relation_tree_saver.rb
index a0452071ccf..ed5392c13d0 100644
--- a/lib/gitlab/import_export/relation_tree_saver.rb
+++ b/lib/gitlab/import_export/relation_tree_saver.rb
@@ -18,7 +18,7 @@ module Gitlab
       def save(tree, dir_path, filename)
         mkdir_p(dir_path)
 
-        tree_json = JSON.generate(tree)
+        tree_json = ::JSON.generate(tree)
 
         File.write(File.join(dir_path, filename), tree_json)
       end
diff --git a/spec/fixtures/lib/gitlab/import_export/invalid_json/project.json b/spec/fixtures/lib/gitlab/import_export/invalid_json/project.json
new file mode 100644
index 00000000000..83cb34eea91
--- /dev/null
+++ b/spec/fixtures/lib/gitlab/import_export/invalid_json/project.json
@@ -0,0 +1,3 @@
+{
+  "invalid" json
+}
diff --git a/spec/frontend/__mocks__/mousetrap/index.js b/spec/frontend/__mocks__/mousetrap/index.js
new file mode 100644
index 00000000000..63c92fa9a09
--- /dev/null
+++ b/spec/frontend/__mocks__/mousetrap/index.js
@@ -0,0 +1,6 @@
+/* global Mousetrap */
+// `mousetrap` uses amd which webpack understands but Jest does not
+// Thankfully it also writes to a global export so we can es6-ify it
+import 'mousetrap';
+
+export default Mousetrap;
diff --git a/spec/javascripts/diffs/components/app_spec.js b/spec/frontend/diffs/components/app_spec.js
similarity index 90%
rename from spec/javascripts/diffs/components/app_spec.js
rename to spec/frontend/diffs/components/app_spec.js
index 5f97182489e..15f91871437 100644
--- a/spec/javascripts/diffs/components/app_spec.js
+++ b/spec/frontend/diffs/components/app_spec.js
@@ -1,6 +1,7 @@
 import Vuex from 'vuex';
 import { shallowMount, createLocalVue } from '@vue/test-utils';
 import { GlLoadingIcon } from '@gitlab/ui';
+import MockAdapter from 'axios-mock-adapter';
 import { TEST_HOST } from 'spec/test_constants';
 import Mousetrap from 'mousetrap';
 import App from '~/diffs/components/app.vue';
@@ -12,14 +13,17 @@ 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 axios from '~/lib/utils/axios_utils';
 import diffsMockData from '../mock_data/merge_request_diffs';
 
 const mergeRequestDiff = { version_index: 1 };
+const TEST_ENDPOINT = `${TEST_HOST}/diff/endpoint`;
 
 describe('diffs/components/app', () => {
   const oldMrTabs = window.mrTabs;
   let store;
   let wrapper;
+  let mock;
 
   function createComponent(props = {}, extendStore = () => {}) {
     const localVue = createLocalVue();
@@ -34,7 +38,7 @@ describe('diffs/components/app', () => {
     wrapper = shallowMount(localVue.extend(App), {
       localVue,
       propsData: {
-        endpoint: `${TEST_HOST}/diff/endpoint`,
+        endpoint: TEST_ENDPOINT,
         endpointMetadata: `${TEST_HOST}/diff/endpointMetadata`,
         endpointBatch: `${TEST_HOST}/diff/endpointBatch`,
         projectPath: 'namespace/project',
@@ -61,8 +65,12 @@ describe('diffs/components/app', () => {
 
   beforeEach(() => {
     // setup globals (needed for component to mount :/)
-    window.mrTabs = jasmine.createSpyObj('mrTabs', ['resetViewContainer']);
-    window.mrTabs.expandViewContainer = jasmine.createSpy();
+    window.mrTabs = {
+      resetViewContainer: jest.fn(),
+    };
+    window.mrTabs.expandViewContainer = jest.fn();
+    mock = new MockAdapter(axios);
+    mock.onGet(TEST_ENDPOINT).reply(200, {});
   });
 
   afterEach(() => {
@@ -71,6 +79,8 @@ describe('diffs/components/app', () => {
 
     // reset component
     wrapper.destroy();
+
+    mock.restore();
   });
 
   describe('fetch diff methods', () => {
@@ -80,15 +90,15 @@ describe('diffs/components/app', () => {
         store.state.notes.discussions = 'test';
         return Promise.resolve({ real_size: 100 });
       };
-      spyOn(window, 'requestIdleCallback').and.callFake(fn => fn());
+      jest.spyOn(window, 'requestIdleCallback').mockImplementation(fn => fn());
       createComponent();
-      spyOn(wrapper.vm, 'fetchDiffFiles').and.callFake(fetchResolver);
-      spyOn(wrapper.vm, 'fetchDiffFilesMeta').and.callFake(fetchResolver);
-      spyOn(wrapper.vm, 'fetchDiffFilesBatch').and.callFake(fetchResolver);
-      spyOn(wrapper.vm, 'setDiscussions');
-      spyOn(wrapper.vm, 'startRenderDiffsQueue');
-      spyOn(wrapper.vm, 'unwatchDiscussions');
-      spyOn(wrapper.vm, 'unwatchRetrievingBatches');
+      jest.spyOn(wrapper.vm, 'fetchDiffFiles').mockImplementation(fetchResolver);
+      jest.spyOn(wrapper.vm, 'fetchDiffFilesMeta').mockImplementation(fetchResolver);
+      jest.spyOn(wrapper.vm, 'fetchDiffFilesBatch').mockImplementation(fetchResolver);
+      jest.spyOn(wrapper.vm, 'setDiscussions').mockImplementation(() => {});
+      jest.spyOn(wrapper.vm, 'startRenderDiffsQueue').mockImplementation(() => {});
+      jest.spyOn(wrapper.vm, 'unwatchDiscussions').mockImplementation(() => {});
+      jest.spyOn(wrapper.vm, 'unwatchRetrievingBatches').mockImplementation(() => {});
       store.state.diffs.retrievingBatches = true;
       store.state.diffs.diffFiles = [];
       wrapper.vm.$nextTick(done);
@@ -236,7 +246,7 @@ describe('diffs/components/app', () => {
       wrapper.vm.fetchData(false);
 
       expect(wrapper.vm.fetchDiffFiles).toHaveBeenCalled();
-      setTimeout(() => {
+      setImmediate(() => {
         expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesMeta).not.toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
@@ -255,7 +265,7 @@ describe('diffs/components/app', () => {
       wrapper.vm.fetchData(false);
 
       expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
-      setTimeout(() => {
+      setImmediate(() => {
         expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesMeta).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesBatch).toHaveBeenCalled();
@@ -272,7 +282,7 @@ describe('diffs/components/app', () => {
       wrapper.vm.fetchData(false);
 
       expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
-      setTimeout(() => {
+      setImmediate(() => {
         expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesMeta).toHaveBeenCalled();
         expect(wrapper.vm.fetchDiffFilesBatch).toHaveBeenCalled();
@@ -350,23 +360,21 @@ describe('diffs/components/app', () => {
       });
 
       // Component uses $nextTick so we wait until that has finished
-      setTimeout(() => {
+      setImmediate(() => {
         expect(store.state.diffs.highlightedRow).toBe('ABC_123');
 
         done();
       });
     });
 
-    it('marks current diff file based on currently highlighted row', done => {
+    it('marks current diff file based on currently highlighted row', () => {
       createComponent({
         shouldShow: true,
       });
 
       // Component uses $nextTick so we wait until that has finished
-      setTimeout(() => {
+      return wrapper.vm.$nextTick().then(() => {
         expect(store.state.diffs.currentDiffFileId).toBe('ABC');
-
-        done();
       });
     });
   });
@@ -403,7 +411,7 @@ describe('diffs/components/app', () => {
     });
 
     // Component uses $nextTick so we wait until that has finished
-    setTimeout(() => {
+    setImmediate(() => {
       expect(store.state.diffs.currentDiffFileId).toBe('ABC');
 
       done();
@@ -449,7 +457,7 @@ describe('diffs/components/app', () => {
 
     describe('visible app', () => {
       beforeEach(() => {
-        spy = jasmine.createSpy('spy');
+        spy = jest.fn();
 
         createComponent({
           shouldShow: true,
@@ -459,21 +467,18 @@ describe('diffs/components/app', () => {
         });
       });
 
-      it('calls `jumpToFile()` with correct parameter whenever pre-defined key is pressed', done => {
-        wrapper.vm
-          .$nextTick()
-          .then(() => {
-            Object.keys(mappings).forEach(function(key) {
-              Mousetrap.trigger(key);
+      it.each(Object.keys(mappings))(
+        'calls `jumpToFile()` with correct parameter whenever pre-defined %s is pressed',
+        key => {
+          return wrapper.vm.$nextTick().then(() => {
+            expect(spy).not.toHaveBeenCalled();
 
-              expect(spy.calls.mostRecent().args).toEqual([mappings[key]]);
-            });
+            Mousetrap.trigger(key);
 
-            expect(spy.calls.count()).toEqual(Object.keys(mappings).length);
-          })
-          .then(done)
-          .catch(done.fail);
-      });
+            expect(spy).toHaveBeenCalledWith(mappings[key]);
+          });
+        },
+      );
 
       it('does not call `jumpToFile()` when unknown key is pressed', done => {
         wrapper.vm
@@ -490,7 +495,7 @@ describe('diffs/components/app', () => {
 
     describe('hideen app', () => {
       beforeEach(() => {
-        spy = jasmine.createSpy('spy');
+        spy = jest.fn();
 
         createComponent({
           shouldShow: false,
@@ -504,7 +509,7 @@ describe('diffs/components/app', () => {
         wrapper.vm
           .$nextTick()
           .then(() => {
-            Object.keys(mappings).forEach(function(key) {
+            Object.keys(mappings).forEach(key => {
               Mousetrap.trigger(key);
 
               expect(spy).not.toHaveBeenCalled();
@@ -520,7 +525,7 @@ describe('diffs/components/app', () => {
     let spy;
 
     beforeEach(() => {
-      spy = jasmine.createSpy();
+      spy = jest.fn();
 
       createComponent({}, () => {
         store.state.diffs.diffFiles = [
@@ -545,15 +550,15 @@ describe('diffs/components/app', () => {
         .then(() => {
           wrapper.vm.jumpToFile(+1);
 
-          expect(spy.calls.mostRecent().args).toEqual(['222.js']);
+          expect(spy.mock.calls[spy.mock.calls.length - 1]).toEqual(['222.js']);
           store.state.diffs.currentDiffFileId = '222';
           wrapper.vm.jumpToFile(+1);
 
-          expect(spy.calls.mostRecent().args).toEqual(['333.js']);
+          expect(spy.mock.calls[spy.mock.calls.length - 1]).toEqual(['333.js']);
           store.state.diffs.currentDiffFileId = '333';
           wrapper.vm.jumpToFile(-1);
 
-          expect(spy.calls.mostRecent().args).toEqual(['222.js']);
+          expect(spy.mock.calls[spy.mock.calls.length - 1]).toEqual(['222.js']);
         })
         .then(done)
         .catch(done.fail);
@@ -602,7 +607,7 @@ describe('diffs/components/app', () => {
 
       expect(wrapper.contains(CompareVersions)).toBe(true);
       expect(wrapper.find(CompareVersions).props()).toEqual(
-        jasmine.objectContaining({
+        expect.objectContaining({
           targetBranch: {
             branchName: 'target-branch',
             versionIndex: -1,
@@ -625,7 +630,7 @@ describe('diffs/components/app', () => {
 
       expect(wrapper.contains(HiddenFilesWarning)).toBe(true);
       expect(wrapper.find(HiddenFilesWarning).props()).toEqual(
-        jasmine.objectContaining({
+        expect.objectContaining({
           total: '5',
           plainDiffPath: 'plain diff path',
           emailPatchPath: 'email patch path',
@@ -663,7 +668,7 @@ describe('diffs/components/app', () => {
     let toggleShowTreeList;
 
     beforeEach(() => {
-      toggleShowTreeList = jasmine.createSpy('toggleShowTreeList');
+      toggleShowTreeList = jest.fn();
     });
 
     afterEach(() => {
diff --git a/spec/frontend/diffs/create_diffs_store.js b/spec/frontend/diffs/create_diffs_store.js
new file mode 100644
index 00000000000..aacde99964c
--- /dev/null
+++ b/spec/frontend/diffs/create_diffs_store.js
@@ -0,0 +1,15 @@
+import Vue from 'vue';
+import Vuex from 'vuex';
+import diffsModule from '~/diffs/store/modules';
+import notesModule from '~/notes/stores/modules';
+
+Vue.use(Vuex);
+
+export default function createDiffsStore() {
+  return new Vuex.Store({
+    modules: {
+      diffs: diffsModule(),
+      notes: notesModule(),
+    },
+  });
+}
diff --git a/spec/frontend/ide/components/pipelines/__snapshots__/list_spec.js.snap b/spec/frontend/ide/components/pipelines/__snapshots__/list_spec.js.snap
index 177cd4559ca..efa58a4a47b 100644
--- a/spec/frontend/ide/components/pipelines/__snapshots__/list_spec.js.snap
+++ b/spec/frontend/ide/components/pipelines/__snapshots__/list_spec.js.snap
@@ -8,6 +8,7 @@ exports[`IDE pipelines list when loaded renders empty state when no latestPipeli
    
   <empty-state-stub
     cansetci="true"
+    class="mb-auto mt-auto"
     emptystatesvgpath="http://test.host"
     helppagepath="http://test.host"
   />
diff --git a/spec/frontend/lib/utils/icon_utils_spec.js b/spec/frontend/lib/utils/icon_utils_spec.js
index 816d634ad15..f798dc6744d 100644
--- a/spec/frontend/lib/utils/icon_utils_spec.js
+++ b/spec/frontend/lib/utils/icon_utils_spec.js
@@ -1,10 +1,14 @@
 import MockAdapter from 'axios-mock-adapter';
 import axios from '~/lib/utils/axios_utils';
-import * as iconUtils from '~/lib/utils/icon_utils';
+import { clearSvgIconPathContentCache, getSvgIconPathContent } from '~/lib/utils/icon_utils';
 
 describe('Icon utils', () => {
   describe('getSvgIconPathContent', () => {
     let spriteIcons;
+    let axiosMock;
+    const mockName = 'mockIconName';
+    const mockPath = 'mockPath';
+    const mockIcons = `<svg><symbol id="${mockName}"><path d="${mockPath}"/></symbol></svg>`;
 
     beforeAll(() => {
       spriteIcons = gon.sprite_icons;
@@ -15,45 +19,63 @@ describe('Icon utils', () => {
       gon.sprite_icons = spriteIcons;
     });
 
-    let axiosMock;
-    let mockEndpoint;
-    const mockName = 'mockIconName';
-    const mockPath = 'mockPath';
-    const getIcon = () => iconUtils.getSvgIconPathContent(mockName);
-
     beforeEach(() => {
       axiosMock = new MockAdapter(axios);
-      mockEndpoint = axiosMock.onGet(gon.sprite_icons);
     });
 
     afterEach(() => {
       axiosMock.restore();
+      clearSvgIconPathContentCache();
     });
 
-    it('extracts svg icon path content from sprite icons', () => {
-      mockEndpoint.replyOnce(
-        200,
-        `<svg><symbol id="${mockName}"><path d="${mockPath}"/></symbol></svg>`,
-      );
+    describe('when the icons can be loaded', () => {
+      beforeEach(() => {
+        axiosMock.onGet(gon.sprite_icons).reply(200, mockIcons);
+      });
 
-      return getIcon().then(path => {
-        expect(path).toBe(mockPath);
+      it('extracts svg icon path content from sprite icons', () => {
+        return getSvgIconPathContent(mockName).then(path => {
+          expect(path).toBe(mockPath);
+        });
+      });
+
+      it('returns null if icon path content does not exist', () => {
+        return getSvgIconPathContent('missing-icon').then(path => {
+          expect(path).toBe(null);
+        });
       });
     });
 
-    it('returns null if icon path content does not exist', () => {
-      mockEndpoint.replyOnce(200, ``);
-
-      return getIcon().then(path => {
-        expect(path).toBe(null);
+    describe('when the icons cannot be loaded on the first 2 tries', () => {
+      beforeEach(() => {
+        axiosMock
+          .onGet(gon.sprite_icons)
+          .replyOnce(500)
+          .onGet(gon.sprite_icons)
+          .replyOnce(500)
+          .onGet(gon.sprite_icons)
+          .reply(200, mockIcons);
       });
-    });
 
-    it('returns null if an http error occurs', () => {
-      mockEndpoint.replyOnce(500);
+      it('returns null', () => {
+        return getSvgIconPathContent(mockName).then(path => {
+          expect(path).toBe(null);
+        });
+      });
 
-      return getIcon().then(path => {
-        expect(path).toBe(null);
+      it('extracts svg icon path content, after 2 attempts', () => {
+        return getSvgIconPathContent(mockName)
+          .then(path1 => {
+            expect(path1).toBe(null);
+            return getSvgIconPathContent(mockName);
+          })
+          .then(path2 => {
+            expect(path2).toBe(null);
+            return getSvgIconPathContent(mockName);
+          })
+          .then(path3 => {
+            expect(path3).toBe(mockPath);
+          });
       });
     });
   });
diff --git a/spec/frontend/mocks/ce/diffs/workers/tree_worker.js b/spec/frontend/mocks/ce/diffs/workers/tree_worker.js
new file mode 100644
index 00000000000..a33ddbbfe63
--- /dev/null
+++ b/spec/frontend/mocks/ce/diffs/workers/tree_worker.js
@@ -0,0 +1,8 @@
+/* eslint-disable class-methods-use-this */
+export default class TreeWorkerMock {
+  addEventListener() {}
+
+  terminate() {}
+
+  postMessage() {}
+}
diff --git a/spec/javascripts/diffs/create_diffs_store.js b/spec/javascripts/diffs/create_diffs_store.js
index aacde99964c..cfefd4238b8 100644
--- a/spec/javascripts/diffs/create_diffs_store.js
+++ b/spec/javascripts/diffs/create_diffs_store.js
@@ -1,15 +1 @@
-import Vue from 'vue';
-import Vuex from 'vuex';
-import diffsModule from '~/diffs/store/modules';
-import notesModule from '~/notes/stores/modules';
-
-Vue.use(Vuex);
-
-export default function createDiffsStore() {
-  return new Vuex.Store({
-    modules: {
-      diffs: diffsModule(),
-      notes: notesModule(),
-    },
-  });
-}
+export { default } from '../../frontend/diffs/create_diffs_store';
diff --git a/spec/lib/gitlab/import_export/json/legacy_reader_spec.rb b/spec/lib/gitlab/import_export/json/legacy_reader_spec.rb
new file mode 100644
index 00000000000..0009a5f81de
--- /dev/null
+++ b/spec/lib/gitlab/import_export/json/legacy_reader_spec.rb
@@ -0,0 +1,149 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::ImportExport::JSON::LegacyReader::User do
+  let(:relation_names) { [] }
+  let(:legacy_reader) { described_class.new(tree_hash, relation_names) }
+
+  describe '#valid?' do
+    subject { legacy_reader.valid? }
+
+    context 'tree_hash not present' do
+      let(:tree_hash) { nil }
+
+      it { is_expected.to be false }
+    end
+
+    context 'tree_hash presents' do
+      let(:tree_hash) { { "issues": [] } }
+
+      it { is_expected.to be true }
+    end
+  end
+end
+
+describe Gitlab::ImportExport::JSON::LegacyReader::File do
+  let(:fixture) { 'spec/fixtures/lib/gitlab/import_export/light/project.json' }
+  let(:project_tree) { JSON.parse(File.read(fixture)) }
+  let(:relation_names) { [] }
+  let(:legacy_reader) { described_class.new(path, relation_names) }
+
+  describe '#valid?' do
+    subject { legacy_reader.valid? }
+
+    context 'given valid path' do
+      let(:path) { fixture }
+
+      it { is_expected.to be true }
+    end
+
+    context 'given invalid path' do
+      let(:path) { 'spec/non-existing-folder/do-not-create-this-file.json' }
+
+      it { is_expected.to be false }
+    end
+  end
+
+  describe '#root_attributes' do
+    let(:path) { fixture }
+
+    subject { legacy_reader.root_attributes(excluded_attributes) }
+
+    context 'No excluded attributes' do
+      let(:excluded_attributes) { [] }
+      let(:relation_names) { [] }
+
+      it 'returns the whole tree from parsed JSON' do
+        expect(subject).to eq(project_tree)
+      end
+    end
+
+    context 'Some attributes are excluded' do
+      let(:excluded_attributes) { %w[milestones labels issues services snippets] }
+      let(:relation_names) { %w[import_type archived] }
+
+      it 'returns hash without excluded attributes and relations' do
+        expect(subject).not_to include('milestones', 'labels', 'issues', 'services', 'snippets', 'import_type', 'archived')
+      end
+    end
+  end
+
+  describe '#consume_relation' do
+    let(:path) { fixture }
+    let(:key) { 'description' }
+
+    context 'block not given' do
+      it 'returns value of the key' do
+        expect(legacy_reader).to receive(:relations).and_return({ key => 'test value' })
+        expect(legacy_reader.consume_relation(key)).to eq('test value')
+      end
+    end
+
+    context 'key has been consumed' do
+      before do
+        legacy_reader.consume_relation(key)
+      end
+
+      it 'does not yield' do
+        expect do |blk|
+          legacy_reader.consume_relation(key, &blk)
+        end.not_to yield_control
+      end
+    end
+
+    context 'value is nil' do
+      before do
+        expect(legacy_reader).to receive(:relations).and_return({ key => nil })
+      end
+
+      it 'does not yield' do
+        expect do |blk|
+          legacy_reader.consume_relation(key, &blk)
+        end.not_to yield_control
+      end
+    end
+
+    context 'value is not array' do
+      before do
+        expect(legacy_reader).to receive(:relations).and_return({ key => 'value' })
+      end
+
+      it 'yield the value with index 0' do
+        expect do |blk|
+          legacy_reader.consume_relation(key, &blk)
+        end.to yield_with_args('value', 0)
+      end
+    end
+
+    context 'value is an array' do
+      before do
+        expect(legacy_reader).to receive(:relations).and_return({ key => %w[item1 item2 item3] })
+      end
+
+      it 'yield each array element with index' do
+        expect do |blk|
+          legacy_reader.consume_relation(key, &blk)
+        end.to yield_successive_args(['item1', 0], ['item2', 1], ['item3', 2])
+      end
+    end
+  end
+
+  describe '#tree_hash' do
+    let(:path) { fixture }
+
+    subject { legacy_reader.send(:tree_hash) }
+
+    it 'parses the JSON into the expected tree' do
+      expect(subject).to eq(project_tree)
+    end
+
+    context 'invalid JSON' do
+      let(:path) { 'spec/fixtures/lib/gitlab/import_export/invalid_json/project.json' }
+
+      it 'raise Exception' do
+        expect { subject }.to raise_exception(Gitlab::ImportExport::Error, 'Incorrect JSON format')
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/import_export/project/tree_loader_spec.rb b/spec/lib/gitlab/import_export/project/tree_loader_spec.rb
deleted file mode 100644
index e683eefa7c0..00000000000
--- a/spec/lib/gitlab/import_export/project/tree_loader_spec.rb
+++ /dev/null
@@ -1,49 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe Gitlab::ImportExport::Project::TreeLoader do
-  let(:fixture) { 'spec/fixtures/lib/gitlab/import_export/with_duplicates.json' }
-  let(:project_tree) { JSON.parse(File.read(fixture)) }
-
-  context 'without de-duplicating entries' do
-    let(:parsed_tree) do
-      subject.load(fixture)
-    end
-
-    it 'parses the JSON into the expected tree' do
-      expect(parsed_tree).to eq(project_tree)
-    end
-
-    it 'does not de-duplicate entries' do
-      expect(parsed_tree['duped_hash_with_id']).not_to be(parsed_tree['array'][0]['duped_hash_with_id'])
-    end
-  end
-
-  context 'with de-duplicating entries' do
-    let(:parsed_tree) do
-      subject.load(fixture, dedup_entries: true)
-    end
-
-    it 'parses the JSON into the expected tree' do
-      expect(parsed_tree).to eq(project_tree)
-    end
-
-    it 'de-duplicates equal values' do
-      expect(parsed_tree['duped_hash_with_id']).to be(parsed_tree['array'][0]['duped_hash_with_id'])
-      expect(parsed_tree['duped_hash_with_id']).to be(parsed_tree['nested']['duped_hash_with_id'])
-      expect(parsed_tree['duped_array']).to be(parsed_tree['array'][1]['duped_array'])
-      expect(parsed_tree['duped_array']).to be(parsed_tree['nested']['duped_array'])
-    end
-
-    it 'does not de-duplicate hashes without IDs' do
-      expect(parsed_tree['duped_hash_no_id']).to eq(parsed_tree['array'][2]['duped_hash_no_id'])
-      expect(parsed_tree['duped_hash_no_id']).not_to be(parsed_tree['array'][2]['duped_hash_no_id'])
-    end
-
-    it 'keeps single entries intact' do
-      expect(parsed_tree['simple']).to eq(42)
-      expect(parsed_tree['nested']['array']).to eq(["don't touch"])
-    end
-  end
-end
diff --git a/spec/lib/gitlab/import_export/project/tree_restorer_spec.rb b/spec/lib/gitlab/import_export/project/tree_restorer_spec.rb
index 9c2b202d5bb..e38ef75d085 100644
--- a/spec/lib/gitlab/import_export/project/tree_restorer_spec.rb
+++ b/spec/lib/gitlab/import_export/project/tree_restorer_spec.rb
@@ -783,7 +783,8 @@ describe Gitlab::ImportExport::Project::TreeRestorer do
     end
 
     before do
-      expect(restorer).to receive(:read_tree_hash) { tree_hash }
+      allow_any_instance_of(Gitlab::ImportExport::JSON::LegacyReader::File).to receive(:valid?).and_return(true)
+      allow_any_instance_of(Gitlab::ImportExport::JSON::LegacyReader::File).to receive(:tree_hash) { tree_hash }
     end
 
     context 'no group visibility' do
diff --git a/spec/lib/gitlab/import_export/relation_tree_restorer_spec.rb b/spec/lib/gitlab/import_export/relation_tree_restorer_spec.rb
index 80901feb893..578418998c0 100644
--- a/spec/lib/gitlab/import_export/relation_tree_restorer_spec.rb
+++ b/spec/lib/gitlab/import_export/relation_tree_restorer_spec.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # This spec is a lightweight version of:
-#   * project_tree_restorer_spec.rb
+#   * project/tree_restorer_spec.rb
 #
 # In depth testing is being done in the above specs.
 # This spec tests that restore project works
@@ -25,7 +25,7 @@ describe Gitlab::ImportExport::RelationTreeRestorer do
     described_class.new(
       user:             user,
       shared:           shared,
-      tree_hash:        tree_hash,
+      relation_reader:  relation_reader,
       importable:       importable,
       object_builder:   object_builder,
       members_mapper:   members_mapper,
@@ -36,14 +36,7 @@ describe Gitlab::ImportExport::RelationTreeRestorer do
 
   subject { relation_tree_restorer.restore }
 
-  context 'when restoring a project' do
-    let(:path) { 'spec/fixtures/lib/gitlab/import_export/complex/project.json' }
-    let(:importable) { create(:project, :builds_enabled, :issues_disabled, name: 'project', path: 'project') }
-    let(:object_builder) { Gitlab::ImportExport::Project::ObjectBuilder }
-    let(:relation_factory) { Gitlab::ImportExport::Project::RelationFactory }
-    let(:reader) { Gitlab::ImportExport::Reader.new(shared: shared) }
-    let(:tree_hash) { importable_hash }
-
+  shared_examples 'import project successfully' do
     it 'restores project tree' do
       expect(subject).to eq(true)
     end
@@ -66,4 +59,18 @@ describe Gitlab::ImportExport::RelationTreeRestorer do
       end
     end
   end
+
+  context 'when restoring a project' do
+    let(:path) { 'spec/fixtures/lib/gitlab/import_export/complex/project.json' }
+    let(:importable) { create(:project, :builds_enabled, :issues_disabled, name: 'project', path: 'project') }
+    let(:object_builder) { Gitlab::ImportExport::Project::ObjectBuilder }
+    let(:relation_factory) { Gitlab::ImportExport::Project::RelationFactory }
+    let(:reader) { Gitlab::ImportExport::Reader.new(shared: shared) }
+
+    context 'using legacy reader' do
+      let(:relation_reader) { Gitlab::ImportExport::JSON::LegacyReader::File.new(path, reader.project_relation_names) }
+
+      it_behaves_like 'import project successfully'
+    end
+  end
 end
diff --git a/spec/services/system_note_service_spec.rb b/spec/services/system_note_service_spec.rb
index 3df620d1fea..5b87ec022ae 100644
--- a/spec/services/system_note_service_spec.rb
+++ b/spec/services/system_note_service_spec.rb
@@ -625,4 +625,14 @@ describe SystemNoteService do
       described_class.discussion_lock(issuable, double)
     end
   end
+
+  describe '.auto_resolve_prometheus_alert' do
+    it 'calls IssuableService' do
+      expect_next_instance_of(::SystemNotes::IssuablesService) do |service|
+        expect(service).to receive(:auto_resolve_prometheus_alert)
+      end
+
+      described_class.auto_resolve_prometheus_alert(noteable, project, author)
+    end
+  end
 end
diff --git a/spec/services/system_notes/issuables_service_spec.rb b/spec/services/system_notes/issuables_service_spec.rb
index c0aaa65971a..477f9eae39e 100644
--- a/spec/services/system_notes/issuables_service_spec.rb
+++ b/spec/services/system_notes/issuables_service_spec.rb
@@ -654,4 +654,16 @@ describe ::SystemNotes::IssuablesService do
           .to eq('resolved the corresponding error and closed the issue.')
     end
   end
+
+  describe '#auto_resolve_prometheus_alert' do
+    subject { service.auto_resolve_prometheus_alert }
+
+    it_behaves_like 'a system note' do
+      let(:action) { 'closed' }
+    end
+
+    it 'creates the expected system note' do
+      expect(subject.note).to eq('automatically closed this issue because the alert resolved.')
+    end
+  end
 end