Getting version output for a file.

Hi,

the Emacs support for git is incomplete, making it bomb out, for example, when doing C-u C-x v =

In order to have it work better, I need to fill in the following functions:

(vc-git-previous-version FILE REV) Return the version number immediately preceding REV for FILE, or nil if there is no previous version.

(vc-git-next-version FILE REV) Return the version number immediately following REV for FILE, or nil if there is no previous version.

REV will tend to be a symbolic reference like "master" or possibly "master{2}" (I am fuzzy about the details, but at least repeated invocations of vc-git-previous-version should work with the previous output). The corresponding next and previous versions should be changes that actually changed the file in question.

There is likely going to be some magic shell invocation of git-rev-list, git-symbolic-ref and/or similar things to achieve this task. I don't have enough of a clue to fill in the necessary details, but I'd be able to convert them into Elisp.

Anybody with good suggestions? It would be beneficial if this would not require the newest git version in order to work. If that means that the output needs to be somewhat more massaged, that's ok.

Thanks,