Hide the "Code for this series" UI in projects that are configured to use git

+1

Alternatively (better than just hiding the ugly wording on the series page): Support linking a series to a specific git branch in the repository that the project is configured to use.

This would be possible, though on the whole we'd prefer to avoid getting series involved in git hosting. It's a lot of complexity that mostly isn't needed, and it brings its own problems: for example, git branches are more freely deletable than bzr branches are (it's just a "git push --delete" rather than a webapp operation) and so it would raise questions such as what happens if the nominated branch for a series is deleted. Best to avoid that if we don't need it.

Now that we have the machinery for per-branch ACLs, it's possible for the webapp to intervene when somebody tries to delete a branch. However, I still have some concerns about that approach: for example, if a project's default repository is an imported repository (which isn't uncommon, e.g. https://launchpad.net/grub), and a series is linked to a branch which is deleted on the remote side, what can we do? We shouldn't fail the import, but it would also be bad for the import to contain a silently-orphaned branch which now cannot be deleted despite not existing on the remote.

I think it would probably be better to have soft links in the same sort of way that we do for merge proposals. We'd check that the branch exists when creating the link, but there'd be nothing to stop it being deleted later, and the UI would only render it as a link if the branch exists. This isn't completely ideal, but I can't think of a better alternative.