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

[Jeff King <peff@peff.net>]

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

> 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