Workaround for bug (feature?) in Git::command_bidi_pipe
command_bidi_pipe doesn't make provision for the case where the git repo is
not in the current working directory. Unlike the other forms of passing
commands to Git.pm, it does not set GIT_DIR or chdir into the working
directory. The functions in Git.pm that rely on command_bidi_pipe also have
this problem.
Also, Git->repository doesn't like being passed a relative path. Git.pm's
_cmd_exec sets GIT_DIR to the relative path and then chdir's into the repo.
Now it tries to access the relative path from inside the repo. Boom.
[change not applicable to this branch, but test changes carried over
- SamV]