Re: Questions about the new

From: Dmitry Potapov <dpotapov@gmail.com>
Date: Oct 12, 2009, 19:03 UTC
Message-ID: <20091012190347.GA26977@dpotapov.dyndns.org>
In-Reply-To: <4AD31EBF.6090307@viscovery.net>

On Mon, Oct 12, 2009 at 02:19:11PM +0200, Johannes Sixt wrote:

> 
> With grafts you can only change parenthood; with replace entries you can
> change parenthood *and* all other aspects of a commit (message, author,
> committer, dates).

Actually, you can. I have written a script that did exactly this. It required to modify parents to point to the new commit. The tricky part was that modification could be on top of other modifications, but I was able to handle this case too. Yet, my script was so hackish that I have never dared to share it with someone (and I used it only couple times during CVS to Git conversion).

> 
> Hence, replace entries are more general than grafts.

I think both mechanism are theoretically equivalent, but with grafts, it was rather difficult to replace objects (but not impossible!).

> The problem with grafts was that, for example, git-pack-objects obeyed the
> graft, and could create a broken repository by removing grafted-away
> objects. And since git-fsck also obeyed the graft, it did not notice the
> breakage.

Moreover, grafted-away objects could be removed by the garbage collector...

Dmitry