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From: Taylor Blau <me@ttaylorr.com>
To: git@vger.kernel.org
Subject: Alternates advertisement on GitHub
Date: Thu, 25 Jul 2019 22:18:40 -0500	[thread overview]
Message-ID: <20190726031840.GB23056@TaylorsMBP9145.attlocal.net> (raw)

Hi everybody,

Pushes to forks of git.git hosted on GitHub now advertise the tips of
git.git as well as branches from your fork.

You may recall that Peff and I have sent a handful of patches to allow
repositories to customize how they gather references to advertise from
an alternate, and then to use those alternate tips as part of the
connectivity check (in [1] and [2], respectively).

GitHub used to advertise '.have's on pushes to forked repositories, but
hasn't done so since 2012. We aggregate data from all forks into a
'network.git', and expose the tips of each fork as:

  refs/remotes/<fork-id>/<refname>

Each fork lists the 'network.git' as its alternate, and thus the
advertisement can get prohibitively large when there are many forks of a
repository.

Michael Haggerty's work on packed refs makes finding references
pertaining only to the root computationally efficient, and [1] makes it
possible to filter down when computing the set of references to
advertise. With [1], we can specify that computation exactly and only
advertise branch tips from the root of a fork network.

We've been slowly rolling this out to a handful of repository networks,
including forks of git.git hosted on GitHub. If you host your fork on
GitHub, you shouldn't notice anything. Hopefully, pushes to your fork
will result in smaller packfiles. In either case, nothing should break;
if it does, please feel free to email me, or support@github.com.

Thanks as well for reviewing both [1] and [2], and making this work
possible. Enjoy :-).

Thanks,
Taylor

[1]: https://public-inbox.org/git/cover.1537466087.git.me@ttaylorr.com/
[2]: https://public-inbox.org/git/20190628101131.GA22862@sigill.intra.peff.net/

             reply	other threads:[~2019-07-26  3:18 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-26  3:18 Taylor Blau [this message]
2019-07-26 13:18 ` Alternates advertisement on GitHub Derrick Stolee
2019-07-26 21:33   ` Taylor Blau

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