Re: Storing state in $GIT_DIR

From: Junio C Hamano <junkio@cox.net>
Date: Aug 26, 2005, 04:31 UTC
Message-ID: <7v3boxl3o1.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <46a038f90508252115415acc04@mail.gmail.com>

Martin Langhoff <martin.langhoff@gmail.com> writes:

Show 7 quoted lines

>> In other words, if you just have a "last commit" pointer in your
>> meta-data, then git is _by_definition_ in sync. There's never anything to
>> get out of sync, because objects aren't going to change.
>
> Hmmm. That repo is in sync, but there are no guarantees that they will
> travel together to a different repo. In fact, the push/pull
> infrastructure wants to push/pull one head at a time.

Wrong as of last week ;-), and definitely wrong since this morning.

> And if they are not in sync, I have no way of knowing. Hmpf. I lie:
> the arch metadata could keep track of what it expects the last head
> commits to be, and complain bitterly if something smells rotten.

What Linus suggests is doable by using an object that can hold a pointer to at least one commit---you used that to record the head commit of the corresponding git branch that the arch metainfo represents.

You only pull arch metainfo branch; the objects associated with the corresponding git branch head will be pulled together when you pull it. You do not have to tell git to pull git-part of the commit chain. There is no need to worry about version skew when you use git this way.

Now, among the existing object types, there are only two kinds of objects you can use for this. If the only thing you need to record is some textual information with one pointer to git branch head, then you can use tag that points at the git head, and store everything else as the tag comment. This is doable but unwieldy.

You could abuse a commit object as well; you store commit objects (such as the corresponding git branch head) as parent commits, and put everything else in a tree that is associated with that commit.