Correct file-header spacing on compare page

Use special classes when is_compare, similar to is_commit. Default
expectation is diff is being viewed in MR

app/assets/stylesheets/framework/files.scss

@@ -4,6 +4,7 @@
  */
 .file-holder {
   border: 1px solid $border-color;
+  border-top: 0;
   border-radius: $border-radius-default;
 
   &.file-holder-no-border {
@@ -328,6 +329,7 @@ span.idiff {
     justify-content: space-between;
     background-color: $gray-light;
     border-bottom: 1px solid $border-color;
+    border-top: 1px solid $border-color;
     padding: 5px $gl-padding;
     margin: 0;
     border-radius: $border-radius-default $border-radius-default 0 0;

app/assets/stylesheets/framework/variables.scss

@@ -490,6 +490,7 @@ $builds-trace-bg: #111;
 */
 $commit-max-width-marker-color: rgba(0, 0, 0, 0);
 $commit-message-text-area-bg: rgba(0, 0, 0, 0);
+$commit-stat-summary-height: 36px;
 
 /*
 * Common
@@ -664,8 +665,14 @@ $priority-label-empty-state-width: 114px;
 Issues Analytics
 */
 $issues-analytics-popover-boarder-color: rgba(0, 0, 0, 0.15);
+
 /*
 Merge Requests
 */
 $mr-tabs-height: 51px;
 $mr-version-controls-height: 56px;
+
+/*
+Compare Branches
+*/
+$compare-branches-sticky-header-height: 68px;

app/assets/stylesheets/pages/diff.scss

@@ -7,22 +7,13 @@
     cursor: pointer;
 
     @media (min-width: map-get($grid-breakpoints, md)) {
+      $mr-file-header-top: $mr-version-controls-height + $header-height + $mr-tabs-height;
+
       position: -webkit-sticky;
       position: sticky;
-      top: $mr-version-controls-height + $header-height + $mr-tabs-height;
-      margin-left: -1px;
-      border-left: 1px solid $border-color;
+      top: $mr-file-header-top;
       z-index: 102;
 
-      &.is-commit {
-        top: $header-height + 36px;
-
-        .with-performance-bar & {
-          top: $header-height + 36px + $performance-bar-height;
-
-        }
-      }
-
       &::before {
         content: '';
         position: absolute;
@@ -35,7 +26,23 @@
       }
 
       .with-performance-bar & {
-        top: $header-height + $performance-bar-height + $mr-version-controls-height + $mr-tabs-height;
+        top: $mr-file-header-top + $performance-bar-height;
+      }
+
+      &.is-commit {
+        top: $header-height + $commit-stat-summary-height;
+
+        .with-performance-bar & {
+          top: $header-height + $commit-stat-summary-height + $performance-bar-height;
+        }
+      }
+
+      &.is-compare {
+        top: $header-height + $compare-branches-sticky-header-height;
+
+        .with-performance-bar & {
+          top: $performance-bar-height + $header-height + $compare-branches-sticky-header-height;
+        }
       }
     }
 

app/views/projects/commit/show.html.haml

@@ -10,7 +10,7 @@
 .container-fluid{ class: [limited_container_width, container_class] }
   = render "commit_box"
   = render "ci_menu"
-  = render "projects/diffs/diffs", diffs: @diffs, environment: @environment, is_commit: true
+  = render "projects/diffs/diffs", diffs: @diffs, environment: @environment, diff_page_context: "is-commit"
 
   .limited-width-notes
     = render "shared/notes/notes_with_form", :autocomplete => true

app/views/projects/compare/show.html.haml

@@ -8,7 +8,7 @@
 
   - if @commits.present?
     = render "projects/commits/commit_list"
-    = render "projects/diffs/diffs", diffs: @diffs, environment: @environment
+    = render "projects/diffs/diffs", diffs: @diffs, environment: @environment, diff_page_context: "is-compare"
   - else
     .card.bg-light
       .center

app/views/projects/diffs/_diffs.html.haml

@@ -2,7 +2,7 @@
 - show_whitespace_toggle = local_assigns.fetch(:show_whitespace_toggle, true)
 - can_create_note = !@diff_notes_disabled && can?(current_user, :create_note, diffs.project)
 - diff_files = diffs.diff_files
-- is_commit = local_assigns.fetch(:is_commit, false)
+- diff_page_context = local_assigns.fetch(:diff_page_context, nil)
 
 .content-block.oneline-block.files-changed.diff-files-changed.js-diff-files-changed
   .files-changed-inner
@@ -25,4 +25,4 @@
   = render 'projects/diffs/warning', diff_files: diffs
 
 .files{ data: { can_create_note: can_create_note } }
-  = render partial: 'projects/diffs/file', collection: diff_files, as: :diff_file, locals: { project: diffs.project, environment: environment, is_commit: is_commit }
+  = render partial: 'projects/diffs/file', collection: diff_files, as: :diff_file, locals: { project: diffs.project, environment: environment, diff_page_context: diff_page_context }

app/views/projects/diffs/_file.html.haml

@@ -1,11 +1,11 @@
 - environment = local_assigns.fetch(:environment, nil)
-- is_commit = local_assigns.fetch(:is_commit, false)
+- diff_page_context = local_assigns.fetch(:diff_page_context, nil)
 - file_hash = hexdigest(diff_file.file_path)
 - image_diff = diff_file.rich_viewer && diff_file.rich_viewer.partial_name == 'image'
 - image_replaced = diff_file.old_content_sha && diff_file.old_content_sha != diff_file.content_sha
 
 .diff-file.file-holder{ id: file_hash, data: diff_file_html_data(project, diff_file.file_path, diff_file.content_sha) }
-  .js-file-title.file-title-flex-parent{ class: is_commit ? "is-commit" : "" }
+  .js-file-title.file-title-flex-parent{ class: diff_page_context }
     .file-header-content
       = render "projects/diffs/file_header", diff_file: diff_file, url: "##{file_hash}"
 

changelogs/unreleased/56938-diff-file-headers-on-compare-not-quite-right.yml

@@ -0,0 +1,5 @@
+---
+title: Correct spacing for comparison page
+merge_request: !24783
+author:
+type: fixed