annotate hgext/blackbox.py @ 48507:58a3be48ddd2

simplemerge: stop merging file flags

As 384df4db6520 (merge: merge file flags together with file content,
2013-01-09) explains, we shouldn't do a 3-way merge of the
symlink. However, since 84614212ae39 (flags: actually merge flags in
simplemerge, 2020-05-16), we do that in
`simplemerge.simplemerge()`. What's more, the merging of the
executable flag there isn't actually necessary; it was made a no-op by
the very next commit, i.e. 4234c9af515d (flags: read flag from
dirstate/disk for workingcopyctx (issue5743), 2020-05-16).

I found the overall flag-merging code (not the bit in
`simplemerge.py`) very hard to follow, but I think I now finally
understand how it works. `mergestate.resolve()` calculates the merged
file flags and sets them on the local side of the merge (confusingly
by calling `_restore_backup()`). Then it calls
`filemerge.filemerge()`, which in turn calls
`simplemerge.simplemerge()` (if premerge is enabled). That means that
the flags on the local side `fcs.flags()` are already correct when the
flag-merging code in `simplemerge.simplemerge()` runs. Interestingly,
that code still works when the local side already has the merged
value, it just doesn't change the value. Here's a truth table to
explain why:

```
BLOMCAR
0000000
0011111
0101011
0111111
1000000
1010000
1100000
1111101
```

B: Base
L: Local
O: Other
M: Merged flags from `mergestate.resolve()`, i.e. what's called "local"
   when we get to `simplemerge.simplemerge()`
C: `commonflags` in `simplemerge.simplemerge()`, i.e. `M & O`
A: `addedflags` in `simplemerge.simplemerge()`, i.e. `(M ^ O) - B`
R: Re-merged flags `simplemerge.simplemerge()`, i.e. `C | A`

As you can see, the re-merged flags are always unchanged compared to
the initial merged flags (R equals M).

Therefore, this patch effectively backs out 84614212ae39. (I might
later refactor this code to have the flags explicitly passed in.)

`simplemerge.simplemerge()` is also called from
`contrib/simplemerge.py`, but that code never passes any flags.

Differential Revision: https://phab.mercurial-scm.org/D11879

# blackbox.py - log repository events to a file for post-mortem debugging
#
# Copyright 2010 Nicolas Dumazet
# Copyright 2013 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.

"""log repository events to a blackbox for debugging

Logs event information to .hg/blackbox.log to help debug and diagnose problems.
The events that get logged can be configured via the blackbox.track and
blackbox.ignore config keys.

Examples::

  [blackbox]
  track = *
  ignore = pythonhook
  # dirty is *EXPENSIVE* (slow);
  # each log entry indicates `+` if the repository is dirty, like :hg:`id`.
  dirty = True
  # record the source of log messages
  logsource = True

  [blackbox]
  track = command, commandfinish, commandexception, exthook, pythonhook

  [blackbox]
  track = incoming

  [blackbox]
  # limit the size of a log file
  maxsize = 1.5 MB
  # rotate up to N log files when the current one gets too big
  maxfiles = 3

  [blackbox]
  # Include nanoseconds in log entries with %f (see Python function
  # datetime.datetime.strftime)
  date-format = %Y-%m-%d @ %H:%M:%S.%f

"""

from __future__ import absolute_import

import re

from mercurial.i18n import _
from mercurial.node import hex

from mercurial import (
    encoding,
    loggingutil,
    registrar,
)
from mercurial.utils import (
    dateutil,
    procutil,
)

# 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 = b'ships-with-hg-core'

cmdtable = {}
command = registrar.command(cmdtable)

configtable = {}
configitem = registrar.configitem(configtable)

configitem(
    b'blackbox',
    b'dirty',
    default=False,
)
configitem(
    b'blackbox',
    b'maxsize',
    default=b'1 MB',
)
configitem(
    b'blackbox',
    b'logsource',
    default=False,
)
configitem(
    b'blackbox',
    b'maxfiles',
    default=7,
)
configitem(
    b'blackbox',
    b'track',
    default=lambda: [b'*'],
)
configitem(
    b'blackbox',
    b'ignore',
    default=lambda: [b'chgserver', b'cmdserver', b'extension'],
)
configitem(
    b'blackbox',
    b'date-format',
    default=b'%Y/%m/%d %H:%M:%S',
)

_lastlogger = loggingutil.proxylogger()


class blackboxlogger(object):
    def __init__(self, ui, repo):
        self._repo = repo
        self._trackedevents = set(ui.configlist(b'blackbox', b'track'))
        self._ignoredevents = set(ui.configlist(b'blackbox', b'ignore'))
        self._maxfiles = ui.configint(b'blackbox', b'maxfiles')
        self._maxsize = ui.configbytes(b'blackbox', b'maxsize')
        self._inlog = False

    def tracked(self, event):
        return (
            b'*' in self._trackedevents and event not in self._ignoredevents
        ) or event in self._trackedevents

    def log(self, ui, event, msg, opts):
        # self._log() -> ctx.dirty() may create new subrepo instance, which
        # ui is derived from baseui. So the recursion guard in ui.log()
        # doesn't work as it's local to the ui instance.
        if self._inlog:
            return
        self._inlog = True
        try:
            self._log(ui, event, msg, opts)
        finally:
            self._inlog = False

    def _log(self, ui, event, msg, opts):
        default = ui.configdate(b'devel', b'default-date')
        date = dateutil.datestr(default, ui.config(b'blackbox', b'date-format'))
        user = procutil.getuser()
        pid = b'%d' % procutil.getpid()
        changed = b''
        ctx = self._repo[None]
        parents = ctx.parents()
        rev = b'+'.join([hex(p.node()) for p in parents])
        if ui.configbool(b'blackbox', b'dirty') and ctx.dirty(
            missing=True, merge=False, branch=False
        ):
            changed = b'+'
        if ui.configbool(b'blackbox', b'logsource'):
            src = b' [%s]' % event
        else:
            src = b''
        try:
            fmt = b'%s %s @%s%s (%s)%s> %s'
            args = (date, user, rev, changed, pid, src, msg)
            with loggingutil.openlogfile(
                ui,
                self._repo.vfs,
                name=b'blackbox.log',
                maxfiles=self._maxfiles,
                maxsize=self._maxsize,
            ) as fp:
                fp.write(fmt % args)
        except (IOError, OSError) as err:
            # deactivate this to avoid failed logging again
            self._trackedevents.clear()
            ui.debug(
                b'warning: cannot write to blackbox.log: %s\n'
                % encoding.strtolocal(err.strerror)
            )
            return
        _lastlogger.logger = self


def uipopulate(ui):
    ui.setlogger(b'blackbox', _lastlogger)


def reposetup(ui, repo):
    # During 'hg pull' a httppeer repo is created to represent the remote repo.
    # It doesn't have a .hg directory to put a blackbox in, so we don't do
    # the blackbox setup for it.
    if not repo.local():
        return

    # Since blackbox.log is stored in the repo directory, the logger should be
    # instantiated per repository.
    logger = blackboxlogger(ui, repo)
    ui.setlogger(b'blackbox', logger)

    # Set _lastlogger even if ui.log is not called. This gives blackbox a
    # fallback place to log
    if _lastlogger.logger is None:
        _lastlogger.logger = logger

    repo._wlockfreeprefix.add(b'blackbox.log')


@command(
    b'blackbox',
    [
        (b'l', b'limit', 10, _(b'the number of events to show')),
    ],
    _(b'hg blackbox [OPTION]...'),
    helpcategory=command.CATEGORY_MAINTENANCE,
    helpbasic=True,
)
def blackbox(ui, repo, *revs, **opts):
    """view the recent repository events"""

    if not repo.vfs.exists(b'blackbox.log'):
        return

    limit = opts.get('limit')
    fp = repo.vfs(b'blackbox.log', b'r')
    lines = fp.read().split(b'\n')

    count = 0
    output = []
    for line in reversed(lines):
        if count >= limit:
            break

        # count the commands by matching lines like: 2013/01/23 19:13:36 root>
        if re.match(br'^\d{4}/\d{2}/\d{2} \d{2}:\d{2}:\d{2} .*> .*', line):
            count += 1
        output.append(line)

    ui.status(b'\n'.join(reversed(output)))