- `Gitlab::Shell.fetch_remote` now takes a `Gitlab::Git::Repository` instead

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13766

* Rename AfterImportService
* Use constants
* Move Git operations to Gitlab::Git::Repository
* Use Regexp.union

Users of project mirrors would see that the number of branches did not
match the number in the branch dropdown because remote branches were
counted when Rugged was in use. With Gitaly, only local branches
are counted.

Closes #36934

Closes gitaly#437

The raw_log method is meant to become the Gitaly RPC boundary. By
setting the defaults before doing the RPC we keep the RPC
implementation simpler. We also sidestep the unfortunate subtleties of
what happens when options[:limit] is not set, or nil.

Closes gitaly#433

Closes gitaly#421

Closes gitaly#415