From: Jeff King <peff@peff.net>
Date: Tue, 12 Jan 2016 18:20:03 GMT
Subject: Re: Can't diff against the 00000000 revision
Message-ID: <20160112182002.GA9244@sigill.intra.peff.net>
In-Reply-To: <jwvr3hmwz1n.fsf-monnier+gmane.comp.version-control.git@gnu.org>

On Tue, Jan 12, 2016 at 11:26:24AM -0500, Stefan Monnier wrote:

> > And hopefully that explains why "000000" does not necessarily make a
> > good placeholder for "the empty thing". There are multiple empty things,
> > and it is not clear what:
> 
> >   git diff 0000000 1234abcd
> 
> > means. Is 0000000 a tree? A blob?
> 
> Well, Git is the one who uses 000000 to refer to an empty thing, but
> indeed it seems like it does inconsistently: it's sometimes used as the
> "empty blob" and sometimes as an "empty tree".

Yes. You can think of it kind of like a NULL pointer; it just means
"nothing". So its meaning is context-dependent. The problem is if we
expect to feed it back to git in a place where the context isn't
obvious.

-Peff