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

Also fix a few tests

so that we don't have to fetch it for non-forks

Signed-off-by: Rémy Coutable <remy@rymai.me>

This helps keep the abstraction layers simpler, and also keep the
interface of those methods consistent, in case of implementation
changes.

Closes gitaly#415

Closes gitaly#355

Submodules have a name in the configuration, but this name is simply
the path at which the submodule was initially checked in (by default
-- the name is totally arbitrary).  If a submodule is moved, it
retains its original name, but its path changes.  Since we discover
submodules inside trees, we have their path but not necessarily their
name.

Make the submodules() function return the submodule hash indexed by
path rather than name, so that renamed submodules can be looked up.
Signed-off-by: David Turner <novalis@novalis.org>