[Nix-dev] Use shallow copying in fetchgit

[Marc Weber]

Excerpts from Peter Simons's message of Wed Jul 20 22:46:57 +0200 2011:
> Does anyone see a problem with applying this patch?

Yes.
At least in the past there was an issue: You could'nt tell git "check
out rev XY". So you had to get trunk and go some revs back. If you use
shallow 1 its very unlikely that trunk is exactly the hash which was
comitted to nixpkgs.

At least that's the only reason you should think about before comitting
it.

If checkout takes too long try nix-repository-manager which creates
.tar.gz archives for git,hg,... VCS sources.

Marc Weber