Merge branch 'new-diff-notes' into 'master'

New diff notes

Fixes #12732, #14731, #19375, #14783 

Builds on https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4110

To do:
- [x] Get it mostly working
- [x] Validate position validity
- [x] Fix: Don’t link to `#`
- [x] Fix: Base ref can be `nil`, potentially, when the MR has an oprhan source branch => Yep, doesn’t work. We need to store a `start_id`
- [x] Optimize: Fewer duplicate `git diff` compares
- [x] Optimize: Pass paths to `PositionTracer#diff` for faster diffs
- [x] Refactor: Use `head_id` in `MergeRequest`/`MergeRequestDiff` instead of `source_sha`
- [x] Refactor: Convert existing array-based diff refs to the DiffRefs model
- [x] Tweak: Use `note_type` in `Autosave` key
- [x] Tweak: Remove `line_code: note.line_code` from `link_to_reply_discussion`
- [x] Update: `SentNotifications` and reply-by-email receiver
- [x] Update: MR diff notification email
- [x] Update: API (MR, Commit note creation and entity)
- [x] Update: GitHub importer
- [x] Address any other TODO comments
- [x] Fix: Suppress "edited 4 minutes ago"
- [x] Write tests
  - [x] `LineMapper`
  - [x] `PositionTracer`
  - [x] `Position`
  - [x] `DiffPositionUpdateService`
  - [x] `DiffNote`
  - [x] `MergeRequests::RefreshService` / `MergeRequest#update_diff_notes_positions`
- [x] Make sure commits with diff notes don't get cleaned up, since this would prevent the diff notes from being rendered (https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5062)

Future improvements:
- Display unresolved comments on files outside the diff, if the comment was added when that file _was_ part of the diff
- Allow commenting on sections between hunks, when expanding the diff using `...`
  - (We'd need to generate line code based on Position if we have it, even if it falls outside bounds of diff)
- `diff_hunk` on diff note API entity
- Show diff hunk in notification email
- Resolved line notes would have a boolean, and be inactive through `notes.any? { !active? || resolved? }`
- Multi line notes would store a number of positions, and do the right thing (™) in grouping and then rendering if the first item is multiline? => true
- Image diff notes could store x,y,width,height instead of old_line,new_line for similar grouping. Does it need a reference to say if it's on old or new? These can't have line_codes, clearly. Rendering would be interesting.
- Show commit line comments in the MR diff
- Comment on specific selected words
- Comment on file header
- Unfold top of discussion diff note
- New diff notes API for commits and MRs

/cc @rspeicher

See merge request !4101

1 files changed, 4 insertions, 4 deletions

diff --git a/spec/controllers/projects/merge_requests_controller_spec.rb b/spec/controllers/projects/merge_requests_controller_spec.rb
index eff74e12869..c4b57e77804 100644
--- a/spec/controllers/projects/merge_requests_controller_spec.rb
+++ b/spec/controllers/projects/merge_requests_controller_spec.rb
@@ -103,7 +103,7 @@ describe Projects::MergeRequestsController do
             id: merge_request.iid,
             format: :patch)
 
-        expect(response.headers['Gitlab-Workhorse-Send-Data']).to start_with("git-format-patch:")
+        expect(response.headers[Gitlab::Workhorse::SEND_DATA_HEADER]).to start_with("git-format-patch:")
       end
     end
   end
@@ -212,7 +212,7 @@ describe Projects::MergeRequestsController do
 
     context 'when the sha parameter matches the source SHA' do
       def merge_with_sha
-        post :merge, base_params.merge(sha: merge_request.source_sha)
+        post :merge, base_params.merge(sha: merge_request.diff_head_sha)
       end
 
       it 'returns :success' do
@@ -229,11 +229,11 @@ describe Projects::MergeRequestsController do
 
       context 'when merge_when_build_succeeds is passed' do
         def merge_when_build_succeeds
-          post :merge, base_params.merge(sha: merge_request.source_sha, merge_when_build_succeeds: '1')
+          post :merge, base_params.merge(sha: merge_request.diff_head_sha, merge_when_build_succeeds: '1')
         end
 
         before do
-          create(:ci_empty_pipeline, project: project, sha: merge_request.source_sha, ref: merge_request.source_branch)
+          create(:ci_empty_pipeline, project: project, sha: merge_request.diff_head_sha, ref: merge_request.source_branch)
         end
 
         it 'returns :merge_when_build_succeeds' do