Changes made to get_push_commits_event_message in
zerver/lib/webhooks/git.py are common to all Git integrations
that use get_push_commits_event_message. These include github,
github_webhook, gitlab, gogs, bitbucket, bitbucket2. In some
cases (for instance, gitlab), no further changes to gitlab/view.py
will be required to support pushing a local branch without commits;
adding a fixture and tests should suffice.