I would use
git rev-parse --verify HEAD
to obtain the SHA1 of the latest commit in the repository.
To get the last commit author:
git log -n1 --format=%an HEAD
It does not really make all that much sense, because you can look up the author by commit, but otherwise to make the author apparent with lookups you might wish to only print the name in lowercase of something along these lines...
works more or less in a same way as svn diff.