annotate hgext/logtoprocess.py @ 34857:84c6b9384d6a

log: add -L/--line-range option to follow file history by line range

We add an experimental -L/--line-range option to 'hg log' taking file patterns
along with a line range using the (new) FILE,FROMLINE-TOLINE syntax where FILE
may be a pattern (matching exactly one file). The resulting history is similar
to what the "followlines" revset except that, if --patch is specified,
only diff hunks within specified line range are shown.

Basically, this brings the CLI on par with what currently only exists in hgweb
through line selection in "file" and "annotate" views resulting in a file log
with filtered patch to only display followed line range.

The option may be specified multiple times and can be combined with --rev and
regular file patterns to further restrict revisions. Usage of this option
requires --follow; revisions are shown in descending order and renames are
followed. Only the --graph option is currently not supported.

The UI is the result of a consensus from review feedback at:

  https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-October/106749.html


The implementation spreads between commands.log() and cmdutil module.
In commands.log(), the main loop may now use a "hunksfilter" factory (similar
to "filematcher") that, for a given "rev", produces a filtering function
for diff hunks for a given file context object.
The logic to build revisions from -L/--line-range options lives in
cmdutil.getloglinerangerevs() which produces "revs", "filematcher" and
"hunksfilter" information. Revisions obtained by following files' line range
are filtered if they do not match the revset specified by --rev option. If
regular FILE arguments are passed along with -L options, both filematchers are
combined into a new matcher.

.. feature::

   Add an experimental -L/--line-range FILE,FROMLINE-TOLINE option to 'hg log'
   command to follow the history of files by line range. In combination with
   -p/--patch option, only diff hunks within specified line range will be
   displayed. Feedback, especially on UX aspects, is welcome.

# 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