hgweb.cgi

exchange: improve computation of relevant markers for large repos

Compute the candidate nodes with relevant markers directly
from keys of the predecessors/successors/children dictionaries of
obsstore. This is faster than iterating over all nodes directly.
This test could be further improved for repositories with relative
few markers compared to the repository size, but this is no longer
hot already. With the current loop structure, the obshashrange use
works as well as before as it passes lists with a single node.

Adjust the interface by allowing revision lists as well as node lists.
This helps cases that computes ancestors as it reduces the
materialisation cost. Use this in _pushdiscoveryobsmarker and
_getbundleobsmarkerpart. Improve the latter further by directly using
ancestors().


Performance benchmarks show notable and welcome improvement to no-op push and
pull (that would also apply to other push/pull). This apply to push and pull
done without evolve.

### push/pull Benchmark parameter
  # bin-env-vars.hg.flavor          = default
  # benchmark.variants.explicit-rev = none
  # benchmark.variants.protocol     = ssh
  # benchmark.variants.revs         = none

 ## benchmark.name                  = hg.command.pull
  # data-env-vars.name              = mercurial-devel-2024-03-22-zstd-sparse-revlog
before: 5.968537 seconds
after:  5.668507 seconds (-5.03%, -0.30)
  # data-env-vars.name              = tryton-devel-2024-03-22-zstd-sparse-revlog
before: 1.446232 seconds
after:  0.835553 seconds (-42.23%, -0.61)
  # data-env-vars.name              = netbsd-src-draft-2024-09-19-zstd-sparse-revlog
before: 5.777412 seconds
after:  2.523454 seconds (-56.32%, -3.25)

 ## benchmark.name                  = hg.command.push
  # data-env-vars.name              = mercurial-devel-2024-03-22-zstd-sparse-revlog
before: 6.155501 seconds
after:  5.885072 seconds (-4.39%, -0.27)

  # data-env-vars.name              = tryton-devel-2024-03-22-zstd-sparse-revlog
before: 1.491054 seconds
after:  0.934882 seconds (-37.30%, -0.56)

  # data-env-vars.name              = netbsd-src-draft-2024-09-19-zstd-sparse-revlog
before: 5.902494 seconds
after:  2.957644 seconds (-49.89%, -2.94)

There is not notable different in these result using the "rust" flavor instead
of the "default".  The performance impact on the same operation when using
evolve were also tested and no impact was noted.

#!/usr/bin/env python3
#
# An example hgweb CGI script, edit as necessary
# See also https://mercurial-scm.org/wiki/PublishingRepositories

# Path to repo or hgweb config to serve (see 'hg help hgweb')
config = b"/path/to/repo/or/config"

# Uncomment and adjust if Mercurial is not installed system-wide
# (consult "installed modules" path from 'hg debuginstall'):
# import sys; sys.path.insert(0, "/path/to/python/lib")

from mercurial import demandimport

demandimport.enable()
from mercurial.hgweb import hgweb, wsgicgi

application = hgweb(config)
wsgicgi.launch(application)