logtoprocess: clean-up old comment

The comment was likely to be for runshellcommand code.

Differential Revision: https://phab.mercurial-scm.org/D1425

hgext/logtoprocess.py

@@ -1,133 +1,131
 # logtoprocess.py - send ui.log() data to a subprocess
 #
 # Copyright 2016 Facebook, Inc.
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 """send ui.log() data to a subprocess (EXPERIMENTAL)
 
 This extension lets you specify a shell command per ui.log() event,
 sending all remaining arguments to as environment variables to that command.
 
 Each positional argument to the method results in a `MSG[N]` key in the
 environment, starting at 1 (so `MSG1`, `MSG2`, etc.). Each keyword argument
 is set as a `OPT_UPPERCASE_KEY` variable (so the key is uppercased, and
 prefixed with `OPT_`). The original event name is passed in the `EVENT`
 environment variable, and the process ID of mercurial is given in `HGPID`.
 
 So given a call `ui.log('foo', 'bar', 'baz', spam='eggs'), a script configured
 for the `foo` event can expect an environment with `MSG1=bar`, `MSG2=baz`, and
 `OPT_SPAM=eggs`.
 
 Scripts are configured in the `[logtoprocess]` section, each key an event name.
 For example::
 
   [logtoprocess]
   commandexception = echo "$MSG2$MSG3" > /var/log/mercurial_exceptions.log
 
 would log the warning message and traceback of any failed command dispatch.
 
 Scripts are run asynchronously as detached daemon processes; mercurial will
 not ensure that they exit cleanly.
 
 """
 
 from __future__ import absolute_import
 
 import itertools
 import os
 import subprocess
 import sys
 
 from mercurial import (
     encoding,
     pycompat,
 )
 
 # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
 # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
 # be specifying the version(s) of Mercurial they are tested with, or
 # leave the attribute unspecified.
 testedwith = 'ships-with-hg-core'
 
 def uisetup(ui):
     if pycompat.iswindows:
         # no fork on Windows, but we can create a detached process
         # https://msdn.microsoft.com/en-us/library/windows/desktop/ms684863.aspx
         # No stdlib constant exists for this value
         DETACHED_PROCESS = 0x00000008
         _creationflags = DETACHED_PROCESS | subprocess.CREATE_NEW_PROCESS_GROUP
 
         def runshellcommand(script, env):
             # we can't use close_fds *and* redirect stdin. I'm not sure that we
             # need to because the detached process has no console connection.
             subprocess.Popen(
                 script, shell=True, env=env, close_fds=True,
                 creationflags=_creationflags)
     else:
         def runshellcommand(script, env):
             # double-fork to completely detach from the parent process
             # based on http://code.activestate.com/recipes/278731
             pid = os.fork()
             if pid:
                 # parent
                 return
             # subprocess.Popen() forks again, all we need to add is
             # flag the new process as a new session.
             if sys.version_info < (3, 2):
                 newsession = {'preexec_fn': os.setsid}
             else:
                 newsession = {'start_new_session': True}
             try:
                 # connect stdin to devnull to make sure the subprocess can't
                 # muck up that stream for mercurial.
                 subprocess.Popen(
                     script, shell=True, stdin=open(os.devnull, 'r'), env=env,
                     close_fds=True, **newsession)
             finally:
                 # mission accomplished, this child needs to exit and not
                 # continue the hg process here.
                 os._exit(0)
 
     class logtoprocessui(ui.__class__):
         def log(self, event, *msg, **opts):
             """Map log events to external commands
 
             Arguments are passed on as environment variables.
 
             """
             script = self.config('logtoprocess', event)
             if script:
                 if msg:
                     # try to format the log message given the remaining
                     # arguments
                     try:
                         # Python string formatting with % either uses a
                         # dictionary *or* tuple, but not both. If we have
                         # keyword options, assume we need a mapping.
                         formatted = msg[0] % (opts or msg[1:])
                     except (TypeError, KeyError):
                         # Failed to apply the arguments, ignore
                         formatted = msg[0]
                     messages = (formatted,) + msg[1:]
                 else:
                     messages = msg
                 # positional arguments are listed as MSG[N] keys in the
                 # environment
                 msgpairs = (
                     ('MSG{0:d}'.format(i), str(m))
                     for i, m in enumerate(messages, 1))
                 # keyword arguments get prefixed with OPT_ and uppercased
                 optpairs = (
                     ('OPT_{0}'.format(key.upper()), str(value))
                     for key, value in opts.iteritems())
                 env = dict(itertools.chain(encoding.environ.items(),
                                            msgpairs, optpairs),
                            EVENT=event, HGPID=str(os.getpid()))
-                # Connect stdin to /dev/null to prevent child processes messing
-                # with mercurial's stdin.
                 runshellcommand(script, env)
             return super(logtoprocessui, self).log(event, *msg, **opts)
 
     # Replace the class for this instance and all clones created from it:
     ui.__class__ = logtoprocessui