hgext/children.py

url: add distribution and version to user-agent request header (BC)

As a server operator, I've always wanted to know what Mercurial
version clients are running so I can track version adoption and
make informed decisions about which versions of Mercurial to
support in extensions. Unfortunately, there is no easy way to discern
this today: the best you can do is look for high-level feature usage
(e.g. bundle2) or sniff capabilities from bundle2 commands. And these
things aren't changed frequently enough to tell you anything that
interesting.

Nearly every piece of software talking HTTP sends its version in
the user agent. This includes web browsers, curl, and even Git.

This patch adds the distribution name and version to the user-agent
HTTP request header. We choose "Mercurial" for the distribution
name because that seems appropriate. The version string comes
from __version__.

The value is inside parenthesis for a few reasons:

* The version *may* contain spaces
* Alternate forms like "Mercurial/<version>" imply structure and
  since the user agent should not be used by servers for protocol
  or feature negotiation/detection, we don't want to even give the
  illusion that the value should be parsed. A free form field is
  the most hostile to parsing.

Flagging the patch as BC so it shows up in release notes. This
change should be backwards compatible. But I wouldn't be surprised if
a server somewhere is filtering on the exact old user agent string. So
I want to make noise about this change.

# Mercurial extension to provide the 'hg children' command
#
# Copyright 2007 by Intevation GmbH <[e-mail]>
#
# Author(s):
# Thomas Arendsen Hein <[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.

'''command to display child changesets (DEPRECATED)

This extension is deprecated. You should use :hg:`log -r
"children(REV)"` instead.
'''

from __future__ import absolute_import

from mercurial.i18n import _
from mercurial import (
    cmdutil,
    commands,
)

templateopts = commands.templateopts

cmdtable = {}
command = cmdutil.command(cmdtable)
# Note for extension authors: ONLY specify testedwith = 'internal' 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 = 'internal'

@command('children',
    [('r', 'rev', '',
     _('show children of the specified revision'), _('REV')),
    ] + templateopts,
    _('hg children [-r REV] [FILE]'),
    inferrepo=True)
def children(ui, repo, file_=None, **opts):
    """show the children of the given or working directory revision

    Print the children of the working directory's revisions. If a
    revision is given via -r/--rev, the children of that revision will
    be printed. If a file argument is given, revision in which the
    file was last changed (after the working directory revision or the
    argument to --rev if given) is printed.

    Please use :hg:`log` instead::

        hg children => hg log -r "children()"
        hg children -r REV => hg log -r "children(REV)"

    See :hg:`help log` and :hg:`help revsets.children`.

    """
    rev = opts.get('rev')
    if file_:
        fctx = repo.filectx(file_, changeid=rev)
        childctxs = [fcctx.changectx() for fcctx in fctx.children()]
    else:
        ctx = repo[rev]
        childctxs = ctx.children()

    displayer = cmdutil.show_changeset(ui, repo, opts)
    for cctx in childctxs:
        displayer.show(cctx)
    displayer.close()