djl/vcprompt — pull request #28 by pjv (2012-10-24 15:16:42+00:00)
Title: fix to return git sha after running garbage collection

if you run `git gc` in a git repo, the garbage collection process removes all the `refs/heads/` files and replaces them with a file called packed-refs in .git. in this case, vcprompt does not return a sha string for the current branch.

this patch modifies the revstring function so that if `refs/heads/` does not exist, instead of immediately returning '', revstring looks for packed-refs, parses it for the correct sha and returns it.