Ship a git-remote-tor helper

Interacting with git remotes over Tor is harder than it needs to be.

The 2 current options I'm aware of are:

• running torsocks git everytime, which is not great;
• setting the http.proxy config option, but
  • this only works for HTTP remotes (not SSH ones, for instance)
  • this works on a per-repository basis
  • it's impossible to cone a repository (or add a remote, or...) and set this configuration item in one step

Given that, I quickly whipped up a git-remote-tor helper (in POSIX SH), which simply runs another git-remote-* helper under torsocks. Using it, it is possible to do things such as git clone tor:http://dccbbv6cooddgcrq.onion/torspec.git.

It currently lacks documentation and doesn't work (yet) with SSH remotes, though.