tests/test-config-env.py

revset: optimize "draft() & ::x" pattern

The `draft() & ::x` type query could be common for selecting one or more
draft feature branches being worked on.

Before this patch, `::x` may travel through the changelog DAG for a long
distance until it gets a smaller revision number than `min(draft())`. It
could be very slow on long changelog with distant (in terms of revision
numbers) drafts.

This patch adds a fast path for this situation, and will stop traveling the
changelog DAG once `::x` hits a non-draft revision.

The fast path also works for `secret()` and `not public()`.

To measure the performance difference, I used drawdag to create a repo that
emulates distant drafts:

          DRAFT4
           |
          DRAFT3 # draft
          /
  PUBLIC9999 # public
      |
  PUBLIC9998
      |
      .   DRAFT2
      .    |
      .   DRAFT1 # draft
      |   /
  PUBLIC0001 # public

And measured the performance using the repo:

  (BEFORE)
  $ hg perfrevset 'draft() & ::(DRAFT2+DRAFT4)'
  ! wall 0.017132 comb 0.010000 user 0.010000 sys 0.000000 (best of 156)
  $ hg perfrevset 'draft() & ::(all())'
  ! wall 0.024221 comb 0.030000 user 0.030000 sys 0.000000 (best of 113)
  (AFTER)
  $ hg perfrevset 'draft() & ::(DRAFT2+DRAFT4)'
  ! wall 0.000243 comb 0.000000 user 0.000000 sys 0.000000 (best of 9303)
  $ hg perfrevset 'draft() & ::(all())'
  ! wall 0.004319 comb 0.000000 user 0.000000 sys 0.000000 (best of 655)

Differential Revision: https://phab.mercurial-scm.org/D441

# Test the config layer generated by environment variables

from __future__ import absolute_import, print_function

import os

from mercurial import (
    encoding,
    rcutil,
    ui as uimod,
    util,
)

testtmp = encoding.environ['TESTTMP']

# prepare hgrc files
def join(name):
    return os.path.join(testtmp, name)

with open(join('sysrc'), 'w') as f:
    f.write('[ui]\neditor=e0\n[pager]\npager=p0\n')

with open(join('userrc'), 'w') as f:
    f.write('[ui]\neditor=e1')

# replace rcpath functions so they point to the files above
def systemrcpath():
    return [join('sysrc')]

def userrcpath():
    return [join('userrc')]

rcutil.systemrcpath = systemrcpath
rcutil.userrcpath = userrcpath
os.path.isdir = lambda x: False # hack: do not load default.d/*.rc

# utility to print configs
def printconfigs(env):
    encoding.environ = env
    rcutil._rccomponents = None # reset cache
    ui = uimod.ui.load()
    for section, name, value in ui.walkconfig():
        source = ui.configsource(section, name)
        print('%s.%s=%s # %s' % (section, name, value, util.pconvert(source)))
    print('')

# environment variable overrides
printconfigs({})
printconfigs({'EDITOR': 'e2', 'PAGER': 'p2'})