bug#63469: 29.0.90; project.el doesn't add menu-bar entries

[Juri Linkov]

>> Sharing between vc and project would be nice.  If possible, this will
>> allow a shorter modeline indicator that will combine vc and project like
>>    --- project-branch ---
>> where the project name replaces the vc-backend name.
>
> That indeed sounds like something that should require specific
> configuration. There can be projects without a branch, or branches without
> "current project".
>
> Or situations like the project root is not the vc root. E.g. when the
> current buffer is in a submodule (so the current branch is submodule's),
> and the project pertains to the parent repository.

The idea is simple: just to replace the backend name by the project name
when the project and its name are non-nil.