bug#25859: 25.1.91; add some branch operations to vc-dir

[Dmitry Gutov]

On 24.02.2017 09:57, Tom Tromey wrote:
> This adds a few branching operations to vc-dir:
>
> * create a branch
> * switch branches
> * show the commit log of a branch
> * remember the branch history in a -history variable
>
> For the commit log it might nice to show it in a buffer whose name
> contains the branch name.  There's a similar bug I opened about making
> the *vc-change-log* buffer per-vc-dir-directory.

Looks great to me, code-wise. Thanks!