Create a todo on failing MR build

When a build fails for a commit, create a todo for the author of the
merge request that commit is the HEAD of. If the commit isn't the HEAD
commit of any MR, don't do anything. If there already is a todo for that
user and MR, don't do anything.

Current limitations:
- This isn't configurable by project.
- The author of a merge request might not be the person who pushed the
  breaking commit.

1 files changed, 25 insertions, 0 deletions

diff --git a/app/services/merge_requests/base_service.rb b/app/services/merge_requests/base_service.rb
index e6837a18696..9d7fca6882d 100644
--- a/app/services/merge_requests/base_service.rb
+++ b/app/services/merge_requests/base_service.rb
@@ -38,5 +38,30 @@ module MergeRequests
     def filter_params
       super(:merge_request)
     end
+
+    def merge_request_from(commit_status)
+      branches = commit_status.ref
+
+      # This is for ref-less builds
+      branches ||= @project.repository.branch_names_contains(commit_status.sha)
+
+      return [] if branches.blank?
+
+      merge_requests = @project.origin_merge_requests.opened.where(source_branch: branches).to_a
+      merge_requests += @project.fork_merge_requests.opened.where(source_branch: branches).to_a
+
+      merge_requests.uniq.select(&:source_project)
+    end
+
+    def each_merge_request(commit_status)
+      merge_request_from(commit_status).each do |merge_request|
+        ci_commit = merge_request.ci_commit
+
+        next unless ci_commit
+        next unless ci_commit.sha == commit_status.sha
+
+        yield merge_request, ci_commit
+      end
+    end
   end
 end