hgdemandimport/tracing.py

templatekw: make {file_*} compare to both merge parents (issue4292)

This redefines the {file_adds}, {file_dels}, {file_mods} template
keywords by getting the lists from the recently introduced context
methods instead of getting them from status compared to p1. As
mentioned before, these are better defined on merge commits. The total
number of files from the three lists now always add up to the number
of files in {files}.

I timed this command:

  hg log -r 4.0::5.0 -T '{rev}\n {file_mods}\n {file_adds}\n {file_dels}\n'

It went from 7.6s to 5.6s with this patch. So it's actually faster
than before.

Note that the "files:" field in the bazaar test log output was using
"{file_mods}" (not "{files}" as one might think based on the label).

Differential Revision: https://phab.mercurial-scm.org/D6369

# Support code for event tracing in Mercurial. Lives in demandimport
# so it can also be used in demandimport.
#
# Copyright 2018 Google LLC.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import

import contextlib
import os

_pipe = None
_checked = False

@contextlib.contextmanager
def log(whencefmt, *whenceargs):
    global _pipe, _session, _checked
    if _pipe is None:
        if _checked:
            yield
            return
        _checked = True
        if 'HGCATAPULTSERVERPIPE' not in os.environ:
            yield
            return
        _pipe = open(os.environ['HGCATAPULTSERVERPIPE'], 'w', 1)
        _session = os.environ.get('HGCATAPULTSESSION', 'none')
    whence = whencefmt % whenceargs
    try:
        # Both writes to the pipe are wrapped in try/except to ignore
        # errors, as we can see mysterious errors in here if the pager
        # is active. Presumably other conditions could trigger
        # problems too.
        try:
            _pipe.write('START %s %s\n' % (_session, whence))
        except IOError:
            pass
        yield
    finally:
        try:
            _pipe.write('END %s %s\n' % (_session, whence))
        except IOError:
            pass