Merge branch '20061-emailsonpushworker-fails-on-new-branch-pushes' into 'master'

Fix emails on push for new and deleted branches

## What does this MR do?

Fix EmailsOnPushWorker when the push is either a new branch or a deleted branch.

## Are there points in the code the reviewer needs to double check?

Don't think so.

## Why was this MR needed? / What are the relevant issue numbers?

Closes #20061.

## Does this MR meet the acceptance criteria?

- ~~[CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added~~ (regression)
- ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- ~~API support added~~
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)


See merge request !5390

app/workers/emails_on_push_worker.rb

@@ -28,12 +28,12 @@ class EmailsOnPushWorker
         :push
       end
 
-    merge_base_sha = project.merge_base_commit(before_sha, after_sha).try(:sha)
-
     diff_refs = nil
     compare = nil
     reverse_compare = false
+
     if action == :push
+      merge_base_sha = project.merge_base_commit(before_sha, after_sha).try(:sha)
       compare = Gitlab::Git::Compare.new(project.repository.raw_repository, before_sha, after_sha)
 
       diff_refs = Gitlab::Diff::DiffRefs.new(

spec/workers/emails_on_push_worker_spec.rb

@@ -12,6 +12,42 @@ describe EmailsOnPushWorker do
   subject { EmailsOnPushWorker.new }
 
   describe "#perform" do
+    context "when push is a new branch" do
+      let(:email) { ActionMailer::Base.deliveries.last }
+
+      before do
+        data_new_branch = data.stringify_keys.merge("before" => Gitlab::Git::BLANK_SHA)
+
+        subject.perform(project.id, recipients, data_new_branch)
+      end
+
+      it "sends a mail with the correct subject" do
+        expect(email.subject).to include("Pushed new branch")
+      end
+
+      it "sends the mail to the correct recipient" do
+        expect(email.to).to eq([user.email])
+      end
+    end
+
+    context "when push is a deleted branch" do
+      let(:email) { ActionMailer::Base.deliveries.last }
+
+      before do
+        data_deleted_branch = data.stringify_keys.merge("after" => Gitlab::Git::BLANK_SHA)
+
+        subject.perform(project.id, recipients, data_deleted_branch)
+      end
+
+      it "sends a mail with the correct subject" do
+        expect(email.subject).to include("Deleted branch")
+      end
+
+      it "sends the mail to the correct recipient" do
+        expect(email.to).to eq([user.email])
+      end
+    end
+
     context "when there are no errors in sending" do
       let(:email) { ActionMailer::Base.deliveries.last }