Re: On writing builtin-reset.c, a question about git-reset.sh

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 20, 2007, 00:24 UTC
Message-ID: <7vir7b9hnv.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <46C8D604.4090203@gmail.com>

Carlos Rica <jasampler@gmail.com> writes:

Show 13 quoted lines

> Hi, I'm writing builtin-reset.c and
> I'm really stuck with a little code in
> git-reset.sh:
>
> if orig=$(git rev-parse --verify HEAD 2>/dev/null)
> then
> 	echo "$orig" >"$GIT_DIR/ORIG_HEAD"
> else
> 	rm -f "$GIT_DIR/ORIG_HEAD"
> fi
>
> My question is about when this condition
> could fail (and then the rm executed),...

When orig does not exist. That is, when HEAD is a symref that point at an unborn branch (e.g. between "git init" and your first "git commit"). After "git reset" of any kind, we would want to make sure that GIT_DIR/ORIG_HEAD points at the commit you were previously at, and if orig is not there we do not want anything in that file.

Another possibility would be if somebody wants to add an unrelated branch to the repository [*1*]. This is against recommended practice, but you could make your HEAD point at an unborn branch using plumbing commands, or even by hand:

	$ echo 'ref: refs/heads/unrelated' >.git/HEAD

Your next commit will make a root commit that is pointed by 'refs/heads/unrelated' ref, but before that happens, we would not want to have GIT_DIR/ORIG_HEAD if you did git-reset.

Now, you might wonder if "git reset" makes any sense from such a state, and actually it does ;-)

	$ git init
        $ git remote add -f friend ../neighbour.git/
        $ git reset --hard friend/master

[Footnote]

*1* People often seem to want to do something like the html, man, and todo branches in my public repository that do not share any history with the primary development branches. Perhaps they think it is cool to do so, but it is not. These independent branches originate from different repositories, and are published in the same repository only for easier distribution. There is no reason for you (nor me) to create such unrelated branches in a single originating repository.

A recommended procedure to publish independent branches in a single repository is to push into one from separate, independent repositories. Starting an independent history in an existing repository, like the main body of this message shows you how, is not recommended.