Modify the branch hooks spec to expect processing of commit messages

Commit messages are not processed for references to issues when
creating the default branch on push. This was expected
behavior (probably to avoid performance problems when first pushing a
repository with thousands of commits). However, this is not an issue
because we always limit the number of commits to process to 100
regardless of whether we are creating the default branch or not.

app/services/git/branch_hooks_service.rb

@@ -20,8 +20,7 @@ module Git
       strong_memoize(:commits) do
         if creating_default_branch?
           # The most recent PROCESS_COMMIT_LIMIT commits in the default branch
-          offset = [count_commits_in_branch - PROCESS_COMMIT_LIMIT, 0].max
-          project.repository.commits(params[:newrev], offset: offset, limit: PROCESS_COMMIT_LIMIT)
+          project.repository.commits(params[:newrev], limit: PROCESS_COMMIT_LIMIT)
         elsif creating_branch?
           # Use the pushed commits that aren't reachable by the default branch
           # as a heuristic. This may include more commits than are actually
@@ -84,9 +83,6 @@ module Git
 
     # Schedules processing of commit messages
     def enqueue_process_commit_messages
-      # don't process commits for the initial push to the default branch
-      return if creating_default_branch?
-
       limited_commits.each do |commit|
         next unless commit.matches_cross_reference_regex?
 

changelogs/unreleased/patch-issue--56683.yml

+---
+title: Process up to 100 commit messages for references when pushing to a new default
+  branch
+merge_request: 29511
+author: Fabio Papa
+type: fixed

spec/services/git/branch_hooks_service_spec.rb

@@ -287,8 +287,8 @@ describe Git::BranchHooksService do
     context 'creating the default branch' do
       let(:oldrev) { Gitlab::Git::BLANK_SHA }
 
-      it 'does not process commit messages' do
-        expect(ProcessCommitWorker).not_to receive(:perform_async)
+      it 'processes a limited number of commit messages' do
+        expect(ProcessCommitWorker).to receive(:perform_async).once
 
         service.execute
       end