Display detached head state in git prompt.
More detailed git prompt information.
Possibility to also display if a branch is behind, has diverged or is up-to-date.
Also changed the implementation to use git-rev-list which is a bit easier than
Allow "staged" as result of parse_git_dirty().
If the corresponding parameter is not set "dirty" will be used as before.
My theme, initial commit.
This is a bit outdated now. Feel free to submit a revised pull-request