customizable subject lines for emails_on_push integration

Problem to solve

I activate "emails on push" at https://gitlab.com/username/reponame/services/emails_on_push/edit and the subject line of the resulting emails is something like [Git][username/reponame][master] first line of commit message

The first part in brackets is not configurable, and is clutter.

Proposal

I would like to have checkboxes in the emails_on_push/edit form to configure the subject line of these emails.

What does success look like, and how can we measure that?

Additional checkboxes to include/exclude

• [Git]
• [username/reponame]
• [branchname]

Possibly a text area for some custom subject line prefix

gitlab-ce41076513 gitlab-ce4107686e gitlab-ce~4107726 ~"feature proposal"