Re: Symbolic refs break ref advertisement on 1.8.4.3+

From: Jeff King <peff@peff.net>
Date: Nov 17, 2013, 10:02 UTC
Message-ID: <20131117100251.GB22166@sigill.intra.peff.net>
In-Reply-To: <CAGyf7-EX2QXKyAwoxv2Ux5cjSp71m-dR+Vq4C3pevJrYaGu42g@mail.gmail.com>

On Sun, Nov 17, 2013 at 01:39:52AM +1100, Bryan Turner wrote:

Show 12 quoted lines

> Aphrael:example bturner$ for ((i=1;i<21;i++)); do git symbolic-ref
> refs/heads/syms/$i refs/heads/master; done
> Aphrael:example bturner$ git ls-remote .
> fatal: protocol error: impossibly long line
> fatal: Could not read from remote repository.
> 
> A symref= entry is written into the first packet of the ref
> advertisement, right after the capabilities, for each symbolic ref in
> the repository. Unfortunately, no splitting is done on that value and
> so once you have 15-20 symbolic refs (more or less depending on path
> lengths), you blow the 996 byte limit in format_packet (pkt-line.c)
> and all further clone/fetch operations fail.

Ick, yeah. I don't think there is a way around that with the way the information is shoe-horned into the protocol. We should probably just revert 5e7dcad (upload-pack: send non-HEAD symbolic refs, 2013-09-17), and assume the HEAD branch name is short enough to fit.

Another option would be to cap the number of non-HEAD symrefs we'd send (by counting up the bytes and keeping below the limit). That at least makes the "easy" cases work, but it's a bit too flaky for my taste.

-Peff