Odd httpheader=1024 required for Phabricator

[Makarius]

On 11/02/2020 03:20, Augie Fackler wrote:
> I guess I'm not sure what's going on here. https://www.mercurial-scm.org/repo/hg/rev/5cda0ce05c42 is the revision that introduced that, but I'm not sure why you need to do anything /to phabricator/ unless it's trying (poorly) to pretend to be an hg server. Is it not just blindly proxying the hg protocol from your hg binary?

Thanks. This hint has helped me to look in the right spots.

Phabricator essentially starts a command-line process to learn about the
server capabilities like this:

  echo capabilities | hg -R .../test-repo serve --stdio

It uses the result for its own http communication. In the output above, there
used to be httpheader=1024 until 4.0.2, but it has disappeared in 4.1.


See also the Phabricator sources:

https://github.com/phacility/phabricator/blob/master/src/applications/diffusion/controller/DiffusionServeController.php#L781

https://github.com/phacility/phabricator/blob/master/src/applications/diffusion/controller/DiffusionServeController.php#L838

https://github.com/phacility/phabricator/blob/master/src/applications/diffusion/protocol/DiffusionMercurialWireProtocol.php#L107

The latter contains further comments about slightly odd censorship of the
capabilities. This is also the place where the workaround is inserted, see
again https://isabelle-dev.sketis.net/T8


A bisection over the hg repository yields the following relevant changeset:

changeset:   30563:e118233172fe
user:        Gregory Szorc <gregory.szorc at gmail.com>
date:        Mon Nov 28 20:46:42 2016 -0800
files:       mercurial/wireproto.py tests/test-ssh-bundle1.t tests/test-ssh.t
description:
wireproto: only advertise HTTP-specific capabilities to HTTP peers (BC)

Previously, the capabilities list was protocol agnostic and we
advertised the same capabilities list to all clients, regardless of
transport protocol.

A few capabilities are specific to HTTP. I see no good reason why we
should advertise them to SSH clients. So this patch limits their
advertisement to HTTP clients.

This patch is BC, but SSH clients shouldn't be using the removed
capabilities so there should be no impact.


What means "BC"?

Maybe Phabricator is a good reason to keep the full information?

Do you think you can refine that for a future release of Mercurial?

In contrast, it is probably difficult to get a patch accepted by the
Phabricator project, because they are only using rather old hg 2.8.2 for their
main installation, and 2.6.2, 3.5.1 in their tests:
https://github.com/phacility/phabricator/blob/master/src/applications/diffusion/protocol/__tests__/DiffusionMercurialWireProtocolTests.php


	Makarius