Dependency on git binary

[andrewbaxter]

Is your feature request related to a problem? Please describe. I'm doing builds in nix and the build environment doesn't have git by default, and I think the git directories too (it might be using an archive tarball). The build fails as is.

Describe the solution you'd like I wouldn't expect this to need git for anything (and I'd like to avoid leaking build environment metadata) - could this be made opt-in?

Describe alternatives you've considered I worked around for now it by setting env var GIT_HASH=fakehash during the build.