When building the source from a checked out tag, eg v1.15, VERSION will
equal v1.15. However, when building from anything other than a tagged
version, you get 'v1.15-4-g50432d5-dirty' meaning I was 4 patches in
front of v1.15, particularly '50432d5' was my current HEAD, and I had
uncommited changes, '-dirty'.
Very useful for folks submitting bug reports on versions they compiled
themselves.
Signed-off-by: Jason Cooper <jason@lakedaemon.net>