hgext/schemes.py

fsmonitor: warn when fsmonitor could be used

fsmonitor can significantly speed up operations on large working
directories. But fsmonitor isn't enabled by default, so naive users
may not realize there is a potential to make Mercurial faster.

This commit introduces a warning to working directory updates when
fsmonitor could be used.

The following conditions must be met:

* Working directory is previously empty
* New working directory adds >= N files (currently 50,000)
* Running on Linux or MacOS
* fsmonitor not enabled
* Warning not disabled via config override

Because of the empty working directory restriction, most users will
only see this warning during `hg clone` (assuming very few users
actually do an `hg up null`).

The addition of a warning may be considered a BC change. However, clone
has printed warnings before. Until recently, Mercurial printed a warning
with the server's certificate fingerprint when it wasn't explicitly
trusted for example. The warning goes to stderr. So it shouldn't
interfere with scripts parsing meaningful output.

The OS restriction was on the advice of Facebook engineers, who only
feel confident with watchman's stability on the supported platforms.

.. feature::

   Print warning when fsmonitor isn't being used on a large repository

Differential Revision: https://phab.mercurial-scm.org/D894

# Copyright 2009, Alexander Solovyov <[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.

"""extend schemes with shortcuts to repository swarms

This extension allows you to specify shortcuts for parent URLs with a
lot of repositories to act like a scheme, for example::

  [schemes]
  py = http://code.python.org/hg/

After that you can use it like::

  hg clone py://trunk/

Additionally there is support for some more complex schemas, for
example used by Google Code::

  [schemes]
  gcode = http://{1}.googlecode.com/hg/

The syntax is taken from Mercurial templates, and you have unlimited
number of variables, starting with ``{1}`` and continuing with
``{2}``, ``{3}`` and so on. This variables will receive parts of URL
supplied, split by ``/``. Anything not specified as ``{part}`` will be
just appended to an URL.

For convenience, the extension adds these schemes by default::

  [schemes]
  py = http://hg.python.org/
  bb = https://bitbucket.org/
  bb+ssh = ssh://[e-mail]/
  gcode = https://{1}.googlecode.com/hg/
  kiln = https://{1}.kilnhg.com/Repo/

You can override a predefined scheme by defining a new scheme with the
same name.
"""
from __future__ import absolute_import

import os
import re

from mercurial.i18n import _
from mercurial import (
    error,
    extensions,
    hg,
    pycompat,
    registrar,
    templater,
    util,
)

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

_partre = re.compile(br'\{(\d+)\}')

class ShortRepository(object):
    def __init__(self, url, scheme, templater):
        self.scheme = scheme
        self.templater = templater
        self.url = url
        try:
            self.parts = max(map(int, _partre.findall(self.url)))
        except ValueError:
            self.parts = 0

    def __repr__(self):
        return '<ShortRepository: %s>' % self.scheme

    def instance(self, ui, url, create):
        url = self.resolve(url)
        return hg._peerlookup(url).instance(ui, url, create)

    def resolve(self, url):
        # Should this use the util.url class, or is manual parsing better?
        try:
            url = url.split('://', 1)[1]
        except IndexError:
            raise error.Abort(_("no '://' in scheme url '%s'") % url)
        parts = url.split('/', self.parts)
        if len(parts) > self.parts:
            tail = parts[-1]
            parts = parts[:-1]
        else:
            tail = ''
        context = dict((str(i + 1), v) for i, v in enumerate(parts))
        return ''.join(self.templater.process(self.url, context)) + tail

def hasdriveletter(orig, path):
    if path:
        for scheme in schemes:
            if path.startswith(scheme + ':'):
                return False
    return orig(path)

schemes = {
    'py': 'http://hg.python.org/',
    'bb': 'https://bitbucket.org/',
    'bb+ssh': 'ssh://[e-mail]/',
    'gcode': 'https://{1}.googlecode.com/hg/',
    'kiln': 'https://{1}.kilnhg.com/Repo/'
    }

def extsetup(ui):
    schemes.update(dict(ui.configitems('schemes')))
    t = templater.engine(lambda x: x)
    for scheme, url in schemes.items():
        if (pycompat.iswindows and len(scheme) == 1 and scheme.isalpha()
            and os.path.exists('%s:\\' % scheme)):
            raise error.Abort(_('custom scheme %s:// conflicts with drive '
                               'letter %s:\\\n') % (scheme, scheme.upper()))
        hg.schemes[scheme] = ShortRepository(url, scheme, t)

    extensions.wrapfunction(util, 'hasdriveletter', hasdriveletter)

@command('debugexpandscheme', norepo=True)
def expandscheme(ui, url, **opts):
    """given a repo path, provide the scheme-expanded path
    """
    repo = hg._peerlookup(url)
    if isinstance(repo, ShortRepository):
        url = repo.resolve(url)
    ui.write(url + '\n')