git: version bump to 2.2.1

The git client has a fairly nasty vulnerability where attackers
can inject arbitrary shell script code into you .git/config, if
you're unlucky enough to be using git in a case-insensitive or
case-normalizing filesystem.  Which, okay, true, doesn't really
affect Linux that much, but it certainly affects OS X and Windows
users.

If you're using the Windows version of Lunar, then you have my
congratulations, because I don't think anyone's ever done that.
I'm pretty sure that there aren't many OSX/Lunar users out there
either.  But it's probably a good idea to keep up to date with
the latest security patches, for whatever reason.
Merge pull request #367 from dagbrown/git-2.2.1

git: version bump to 2.2.1