git: suggest local branches for push

[Trojan295]

This PR changes to completion of git push to suggest local branches instead of remote branches.

To me, the current approach to show remote branches is not useful, because it suggests to push remote branches to remotes. The command git-push syntax per documentation is:

<refspec>…​

Specify what destination ref to update with what source object. The format of a parameter is an optional plus +, followed by the source object , followed by a colon :, followed by the destination ref .

So IMO, after the repository argument, carapace should suggest local branches, as the refspec starts with the source object.