On 6/29/2019 3:55 AM, Jeff King wrote:
> On Fri, Jun 28, 2019 at 09:22:56AM -0700, Junio C Hamano wrote:
>
>>> argv_array_push(&rev_list.args, "--quiet");
>>> + argv_array_push(&rev_list.args, "--alternate-refs");
>>> if (opt->progress)
>>> argv_array_pushf(&rev_list.args, "--progress=%s",
>>> _("Checking connectivity"));
>>
>> Quite honestly, I am very surprised that we did not do this. The
>> idea of alternate object store, as well as reducing transfer cost by
>> advertising their tips as '.have' phony refs, is almost as old as
>> the pack protocol itself.
>
> Yeah, as you note we are already telling the other side of the push
> "hey, we already have these objects". So we are almost always just
> walking over our own local objects in the connectivity check, which is
> silly.
>
> I only did "clone --reference" in the perf test because it was the
> simplest, but a push to a server with alternates should be similarly
> improved. E.g., doing this in a clone of linux.git:
>
> git init --bare dst.git
> echo '../../.git/objects' >dst.git/objects/info/alternates
> time git push dst.git HEAD
>
> goes from 40+ seconds to 100ms or so. Again, obviously that's the best
> case, but it should also improve the normal case of somebody pulling
> down "torvalds/linux.git" and pushing it back up to their own
> "peff/linux.git", too.
>
> I don't have real-world numbers yet from GitHub, because we're not
> actually advertising .haves on push right now. All of the Git pieces are
> now in places to do so, but we still have to make some tweaks at our
> replication layer. But soon. :)
Exciting! Should improve the user's experience keeping their forks
updated!
-Stolee
