Re: http-protocol question

> On Tue, Dec 2, 2014 at 2:34 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:
>> Hi Bryan,
>>
>> Bryan Turner wrote:
>>
>>> Is there actually logic somewhere in Git that does that "MAY walk
>>> backwards" step?
>>
>> Yes.  See upload-pack.c::check_non_tip and
>> http://thread.gmane.org/gmane.comp.version-control.git/178814.
>
> Jonathan,
>
> Thanks for the reply! I realize now I didn't really cite the part of
> that documentation that I'm most interested in, which is: "through
> history _or through the reflog_". It's the reflog bit I'm looking for.
> Sorry for not being more clear. check_non_tip appears to look at
> ancestry, walking back up (or down, depending on your view) the DAG to
> see if the requested SHA-1 is reachable from a current ref, so it
> looks like that's covering the "through history" part of that blurb.
>
> The reason I ask is that there is a race condition that exists where
> the ref advertisement lists refs/heads/foo at abc1234, and then foo is
> deleted before the actual upload-pack request comes in. In that
> situation, walking backwards through _history_ will only allow the
> upload-pack to complete unless the deleted ref was merged into another

> ref prior to being deleted (if I understand the code correctly). It
> seems like looking at the reflogs, and seeing that refs/heads/foo did
> in fact exist and did in fact refer to abc1234, is the only approach
> that could allow the upload-pack to complete. The documentation hints
> that such a thing is possible, but I don't see any code in Git that
> seems to do that.
>
> Does that make more sense? Does that functionality exist and I've just
> overlooked it?
>
> Thanks again,
> Bryan Turner
>
>>
>> Hope that helps,
>> Jonathan