Show more differences with upstream about vcprompt

[djl]

This isn't something I'd ever use personally (in fact, I only use two or three features in vcprompt as it is), maybe somebody will find it useful.

IMO, it would probably make more sense to do this in a separate little shell script or even combine vcprompt + git bash prompt. This would be faster than having to fork out to git with Python.

For example:

VCPROMPT_FORMAT=' (%s:%b%m%u)'
GIT_PS1_SHOWUPSTREAM="verbose"
PS1="$(vcprompt)$(__git_ps1)"

I have no idea if that will work as I've never used __git_ps1 but you get the idea.

But with all that said, if you provide a pull request it'll be harder for me to immediately say no :)