Merge branch 'fix/reduce-number-of-ref-exists-calls' into 'master'

Check for keep-around commits once if target and source projects are the same

Closes #37439 and gitaly#1000

See merge request gitlab-org/gitlab-ce!16972

app/models/merge_request_diff.rb

@@ -290,7 +290,7 @@ class MergeRequestDiff < ActiveRecord::Base
   end
 
   def keep_around_commits
-    [repository, merge_request.source_project.repository].each do |repo|
+    [repository, merge_request.source_project.repository].uniq.each do |repo|
       repo.keep_around(start_commit_sha)
       repo.keep_around(head_commit_sha)
       repo.keep_around(base_commit_sha)

app/services/merge_requests/create_service.rb

@@ -9,11 +9,8 @@ module MergeRequests
       merge_request.source_branch = params[:source_branch]
       merge_request.merge_params['force_remove_source_branch'] = params.delete(:force_remove_source_branch)
 
-      # n+1: https://gitlab.com/gitlab-org/gitlab-ce/issues/37439
-      Gitlab::GitalyClient.allow_n_plus_1_calls do
       create(merge_request)
     end
-    end
 
     def before_create(merge_request)
       # current_user (defined in BaseService) is not available within run_after_commit block