hg

showstack: also handle SIGALRM

This is looking *very* handy when debugging mysterious hangs in a
test: you can wrap a hanging invocation in

  `perl -e 'alarm shift @ARGV; exec @ARGV' 1`

for example, a hanging `hg pull` becomes

  `perl -e 'alarm shift @ARGV; exec @ARGV' 1 hg pull`

where the `1` is the timeout in seconds before the process will be hit
with SIGALRM. After making that edit to the test file, you can then
use --extra-config-opt on run-tests.py to globaly enable showstack
during the test run, so you'll get full stack traces as you force your
hg to exit.

I wonder (but only a little, not enough to take action just yet) if we
should wire up some scaffolding in run-tests itself to automatically
wrap all commands in alarm(3) somehow to avoid hangs in the future?

Differential Revision: https://phab.mercurial-scm.org/D4870

#!/usr/bin/env python
#
# mercurial - scalable distributed SCM
#
# Copyright 2005-2007 Matt Mackall <[e-mail]>
#
# 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 os
import sys

if os.environ.get('HGUNICODEPEDANTRY', False):
    try:
        reload(sys)
        sys.setdefaultencoding("undefined")
    except NameError:
        pass

libdir = '@LIBDIR@'

if libdir != '@' 'LIBDIR' '@':
    if not os.path.isabs(libdir):
        libdir = os.path.join(os.path.dirname(os.path.realpath(__file__)),
                              libdir)
        libdir = os.path.abspath(libdir)
    sys.path.insert(0, libdir)

from hgdemandimport import tracing
with tracing.log('hg script'):
    # enable importing on demand to reduce startup time
    try:
        if sys.version_info[0] < 3 or sys.version_info >= (3, 6):
            import hgdemandimport; hgdemandimport.enable()
    except ImportError:
        sys.stderr.write("abort: couldn't find mercurial libraries in [%s]\n" %
                         ' '.join(sys.path))
        sys.stderr.write("(check your install and PYTHONPATH)\n")
        sys.exit(-1)

    from mercurial import dispatch
    dispatch.run()