Re: [PATCH] fetch-pack: fix object_id of exact sha1

From: Jeff King <peff@peff.net>
Date: Feb 29, 2016, 09:50 UTC
Message-ID: <20160229095041.GA2950@sigill.intra.peff.net>
In-Reply-To: <xmqqh9gseiqk.fsf@gitster.mtv.corp.google.com>

On Sun, Feb 28, 2016 at 11:29:39AM -0800, Junio C Hamano wrote:

Show 30 quoted lines

> Gabriel Souza Franco <gabrielfrancosouza@gmail.com> writes:
> 
> >>>       struct object_id oid;
> >>>
> >>> -     if (!get_oid_hex(name, &oid) && name[GIT_SHA1_HEXSZ] == ' ')
> >>> -             name += GIT_SHA1_HEXSZ + 1;
> >>> -     else
> >>> +     if (get_oid_hex(name, &oid))
> >>>               oidclr(&oid);
> >>> +     else if (name[GIT_SHA1_HEXSZ] == ' ')
> >>> +             name += GIT_SHA1_HEXSZ + 1;
> >>
> >> This makes sense to me. I wonder if we should be more particular about
> >> the pure-sha1 case consuming the whole string, though. E.g., if we get:
> >>
> >>   1234567890123456789012345678901234567890-bananas
> >>
> >> that should probably not have sha1 1234...
> >>
> >> I don't think it should ever really happen in practice, but it might be
> >> worth noticing and complaining when name[GIT_SHA1_HEXSZ] is neither
> >> space nor '\0'.
> >
> > Right. What kind of complaining? Is doing oidclr(&oid) and letting it
> > fail elsewhere enough?
> 
> I think that is the most sensible.  After all, the first get-oid-hex
> expects to find a valid 40-hex object name at the beginning of line,
> and oidclr() is the way for it to signal a broken input, which is
> how the callers of this codepath expects errors to be caught.

Actually, I think we _don't_ want to signal an error here, but checking for '\0' is still the right thing to do.

Once upon a time, fetch-pack took just the names of refs, like:

  git fetch-pack $remote refs/heads/foo

and the same format was used for --stdin. Then in 58f2ed0 (remote-curl: pass ref SHA-1 to fetch-pack as well, 2013-12-05), it learned to take "$sha1 $ref". But if we didn't see a sha1, then we continued to treat it as a refname.

This patch adds a new format, just "$sha1". So if get_oid_hex() succeeds _and_ we see '\0', we know we have that case. But if we don't see '\0', then we should assume it's a refname (e.g., "1234abcd...-bananas").

I think in practice it shouldn't matter much, as callers should be feeding fully qualified refs (and we document this). However, we still want to distinguish so that we give the correct error ("no such remote ref 1234abcd...-bananas", not "whoops, the other side doesn't have 1234abcd").

-Peff