Merge branch 'n-plus-1-notice' into 'master'

Adds a Gitaly n+1 notice to commit handling on access check

See merge request gitlab-org/gitlab-ee!3034

lib/gitlab/checks/change_access.rb

@@ -162,6 +162,8 @@ module Gitlab
           # if newrev is blank, the branch was deleted
           return if deletion? || !(commit_validation || validate_path_locks?)
 
+          # n+1: https://gitlab.com/gitlab-org/gitlab-ee/issues/3593
+          Gitlab::GitalyClient.allow_n_plus_1_calls do
             commits.each do |commit|
               if commit_validation
                 error = check_commit(commit, push_rule)
@@ -174,6 +176,7 @@ module Gitlab
             end
           end
         end
+      end
 
       def branch_name_allowed_by_push_rule?(push_rule)
         return true unless push_rule