fix mass SQL statements on initial push

This commit disables process_commit_messages()
for the initial push to the default branch.
This fixes the mass SQL statements (~500000) that were executed during
the initial push of the linux kernel for example.

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 7.9.0 (unreleased)
+  - Fix mass SQL statements on initial push (Hannes Rosenögger)
   - Add tag push notifications and normalize HipChat and Slack messages to be consistent (Stan Hu)
   - Add comment notification events to HipChat and Slack services (Stan Hu)
   - Add issue and merge request events to HipChat and Slack services (Stan Hu)

app/services/git_push_service.rb

@@ -42,8 +42,10 @@ class GitPushService
           # as a heuristic. This may include more commits than are actually pushed, but
           # that shouldn't matter because we check for existing cross-references later.
           @push_commits = project.repository.commits_between(project.default_branch, newrev)
-        end
+
+          # don't process commits for the initial push to the default branch
           process_commit_messages(ref)
+        end
       elsif push_to_existing_branch?(ref, oldrev)
         # Collect data for this git push
         @push_commits = project.repository.commits_between(oldrev, newrev)

spec/services/git_push_service_spec.rb

@@ -197,15 +197,6 @@ describe GitPushService do
 
       service.execute(project, user, @blankrev, @newrev, 'refs/heads/other')
     end
-
-    it "finds references in the first push to a default branch" do
-      allow(project.repository).to receive(:commits_between).with(@blankrev, @newrev).and_return([])
-      allow(project.repository).to receive(:commits).with(@newrev).and_return([commit])
-
-      expect(Note).to receive(:create_cross_reference_note).with(issue, commit, commit_author, project)
-
-      service.execute(project, user, @blankrev, @newrev, 'refs/heads/master')
-    end
   end
 
   describe "closing issues from pushed commits" do