Re: [RFC][PATCH] Rewriting revs in place in push target repository

From: Linus Torvalds <torvalds@osdl.org>
Date: Aug 14, 2005, 02:10 UTC
Message-ID: <Pine.LNX.4.58.0508131859190.3553@g5.osdl.org>
In-Reply-To: <7vwtmpjq17.fsf@assigned-by-dhcp.cox.net>

On Sat, 13 Aug 2005, Junio C Hamano wrote:

Show 11 quoted lines

>
> Petr Baudis <pasky@suse.cz> writes: 
> > Rewrite refs in place in receive-pack & friends
> >
> > When updating a ref, it would write a new file with the new ref and
> > then rename it, overwriting the original file. The problem is that
> > this destroys permissions and ownership of the original file, which is
> > troublesome especially in multiuser environment, like the one I live in.
> 
> Hmph.  If a repo is _really_ used multiuser then you should not
> have to care about ownership.

I think Pasky's usage is that different heads are owned by different groups and/or users, and he wants to use the filesystem permissions to determine who gets to update which branch. Which is reasonable in a way.

On the other hand, I don't think filesystem permissions are really very useful. I think it's more appropriate to use triggers to say something like "only allow people in the 'xyz' group to write to this head".

Obviously, triggers aren't about _security_ - somebody who has write permissions to the tree can always screw up others. But triggers are fine for things like branch ownership, where you trust your users, but you just want to avoid mistakes.

So a trigger might be something like

	#!/bin/sh
	. git-sh-setup-script
	branch="$1"
	old="$2"
	new="$3"
	if [ -e $GIT_DIR/permissions/$branch ]; then
		id=$(id -un)
		grep -q "^$id$" $GIT_DIR/permissions/$branch ||
			die "You're not allowed to write to $branch"
	fi
	true

and that would allow you to list all users that are allowed to write to the branch in $GIT_DIR/permissions/<branchname>.

Totally untested, of course. But the concept should work.

		Linus