Merge branch 'fix-commits-manual-merge' into 'master'

Fix bug where manually merged branches in a MR would end up with an empty diff

This bug manifested in 8.1 with the refactoring of `RefreshService`. Here's what happens:

1. User create a new branch `foo`.
2. User creates a merge request for `foo`.
3. User merges `foo` into `master` by hand.
4. `RefreshService` reloads the merge request. Since `master` is equivalent to `foo`, this results in an empty diff.
5. `RefreshService` then closes the MR.

This wasn't an issue when you use the normal "Accept Merge Request" flow because the act of clicking the button closes the merge request, so step 4 never happens.

Closes #3314

See merge request !1758

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
+v 8.2.0 (unreleased)
+  - Fix bug where manually merged branches in a MR would end up with an empty diff (Stan Hu)
+  - Force update refs/merge-requests/X/head upon a push to the source branch of a merge request (Stan Hu)
+  - Improved performance of finding users by one of their Email addresses
+  - Improved performance of replacing references in comments
+  - Show last project commit to default branch on project home page
+  - Highlight comment based on anchor in URL
+  - Adds ability to remove the forked relationship from project settings screen. (Han Loong Liauw)
+  - Improved performance of sorting milestone issues
+  - Allow users to select the Files view as default project view (Cristian Bica)
+  - Show "Empty Repository Page" for repository without branches (Artem V. Navrotskiy)
+  - Fix: Inability to reply to code comments in the MR view, if the MR comes from a fork
+  - Use git follow flag for commits page when retrieve history for file or directory
+  - Show merge request CI status on merge requests index page
+  - Extend yml syntax for only and except to support specifying repository path
+  - Enable shared runners to all new projects
+  - Fix: 500 error returned if destroy request without HTTP referer (Kazuki Shimizu)
+  - Remove deprecated CI events from project settings page
+  - Use issue editor as cross reference comment author when issue is edited with a new mention.
+  - [API] Add ability to fetch the commit ID of the last commit that actually touched a file
+  - Add "New file" link to dropdown on project page
+  - Include commit logs in project search
+  - Add "added", "modified" and "removed" properties to commit object in webhook
+  - Rename "Back to" links to "Go to" because its not always a case it point to place user come from
+  - Allow groups to appear in the search results if the group owner allows it
+
 v 8.1.3
   - Force update refs/merge-requests/X/head upon a push to the source branch of a merge request (Stan Hu)
   - Spread out runner contacted_at updates

app/services/merge_requests/refresh_service.rb

@@ -7,17 +7,17 @@ module MergeRequests
       @branch_name = Gitlab::Git.ref_name(ref)
 
       find_new_commits
+      # Be sure to close outstanding MRs before reloading them to avoid generating an
+      # empty diff during a manual merge
+      close_merge_requests
       reload_merge_requests
 
       # Leave a system note if a branch was deleted/added
       if branch_added? || branch_removed?
         comment_mr_branch_presence_changed
-        comment_mr_with_commits
-      else
-        comment_mr_with_commits
-        close_merge_requests
       end
 
+      comment_mr_with_commits
       execute_mr_web_hooks
 
       true

spec/services/merge_requests/refresh_service_spec.rb

@@ -62,6 +62,25 @@ describe MergeRequests::RefreshService do
       it { expect(@fork_merge_request.notes.last.note).to include('changed to merged') }
     end
 
+    context 'manual merge of source branch' do
+      before do
+        # Merge master -> feature branch
+        author = { email: 'test@gitlab.com', time: Time.now, name: "Me" }
+        commit_options = { message: 'Test message', committer: author, author: author }
+        master_commit = @project.repository.commit('master')
+        @project.repository.merge(@user, master_commit.id, 'feature', commit_options)
+        commit = @project.repository.commit('feature')
+        service.new(@project, @user).execute(@oldrev, commit.id, 'refs/heads/feature')
+        reload_mrs
+      end
+
+      it { expect(@merge_request.notes.last.note).to include('changed to merged') }
+      it { expect(@merge_request).to be_merged }
+      it { expect(@merge_request.diffs.length).to be > 0 }
+      it { expect(@fork_merge_request).to be_merged }
+      it { expect(@fork_merge_request.notes.last.note).to include('changed to merged') }
+    end
+
     context 'push to fork repo source branch' do
       let(:refresh_service) { service.new(@fork_project, @user) }
       before do