[UPDATE] Plugin: git — fix #1500, fix #1504, fix #1546, fix #1966, fix #2546, fix #2714

## Update branch

**Plugin:** `git`

This branch contains updates for the `git` plugin.

## Status

I am still looking through all the open issues, and will add more stuff concerning the `git` plugin. After that we should allow some time for testing.

@Stibbons maybe you wish to help or to manage the branch yourself? @robbyrussell is that what you meant in #2771 about merging _"a collection"_ of PRs? — or _"one PR to rule them all"_?

Also, I think the auto-closing feature should kick in when this is merged, which will ease maintenance.

## Changelog

* Fixes #1500
* Fixes #1504
* Fixes #1546
* Fixes #1966
* Fixes #2546
* Fixes #2714