Turn off the annoying "loose objects" warning

[prati0100]

The discussion over at [0] suggested that we should probably stop showing the annoying the dialog on startup, and instead start doing auto-gc. Since git-gui mostly uses plumbing commands, auto-gc is not triggered. But it is a pretty good idea to use it.

I have an almost complete implementation over at [1]. I'll try to finish up a few loose ends and send it soon.

[0] https://public-inbox.org/git/[email protected]/ [1] https://github.com/prati0100/git-gui/tree/py/auto-gc