Get rid of commit_zero

[sarum9in]

The current revision implementation is not related to commit_zero at all, it is just the path from the root, I think we don't care as much what revision value is as long as it is incrementing for a particular version, so I am considering to remove commit_zero.

TODO discuss and make sure that it works as expected

[sarum9in]

OK, now I understand how this works. We rely on git-describe that apparently implicitly uses first available tag. And while this works, it is not perfect in a sense that if we commit something to master, e.g. LICENSE.build, we break consequent revisions.

[sarum9in]

My proposal is to use git rev-list --count HEAD. This is consistent with PKGBUILD practice from AUR: echo $(git rev-list --count HEAD).$(git rev-parse --short HEAD).

Advantages:

• This does not rely on artificial tags. Normally named tag creates a release on github, this is misleading.
• It will always preserve version increments regardless of what we do in other branches.

Disadvantages:

• Numbers will be slightly more arbitrary. However they already are :/ Do we really want to keep this property?

@jpakkane I would appreciate if you take a look.