mercurial/pycompat.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.

# pycompat.py - portability shim for python 3
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""Mercurial portability shim for python 3.

This contains aliases to hide python version-specific details from the core.
"""

from __future__ import absolute_import

import sys

if sys.version_info[0] < 3:
    import cPickle as pickle
    import cStringIO as io
    import httplib
    import Queue as _queue
    import SocketServer as socketserver
    import urlparse
    import xmlrpclib
else:
    import http.client as httplib
    import io
    import pickle
    import queue as _queue
    import socketserver
    import urllib.parse as urlparse
    import xmlrpc.client as xmlrpclib

stringio = io.StringIO
empty = _queue.Empty
queue = _queue.Queue

class _pycompatstub(object):
    pass

def _alias(alias, origin, items):
    """ populate a _pycompatstub

    copies items from origin to alias
    """
    def hgcase(item):
        return item.replace('_', '').lower()
    for item in items:
        try:
            setattr(alias, hgcase(item), getattr(origin, item))
        except AttributeError:
            pass

httpserver = _pycompatstub()
urlreq = _pycompatstub()
urlerr = _pycompatstub()
try:
    import BaseHTTPServer
    import CGIHTTPServer
    import SimpleHTTPServer
    import urllib2
    import urllib
    _alias(urlreq, urllib, (
        "addclosehook",
        "addinfourl",
        "ftpwrapper",
        "pathname2url",
        "quote",
        "splitattr",
        "splitpasswd",
        "splitport",
        "splituser",
        "unquote",
        "url2pathname",
        "urlencode",
        "urlencode",
    ))
    _alias(urlreq, urllib2, (
        "AbstractHTTPHandler",
        "BaseHandler",
        "build_opener",
        "FileHandler",
        "FTPHandler",
        "HTTPBasicAuthHandler",
        "HTTPDigestAuthHandler",
        "HTTPHandler",
        "HTTPPasswordMgrWithDefaultRealm",
        "HTTPSHandler",
        "install_opener",
        "ProxyHandler",
        "Request",
        "urlopen",
    ))
    _alias(urlerr, urllib2, (
        "HTTPError",
        "URLError",
    ))
    _alias(httpserver, BaseHTTPServer, (
        "HTTPServer",
        "BaseHTTPRequestHandler",
    ))
    _alias(httpserver, SimpleHTTPServer, (
        "SimpleHTTPRequestHandler",
    ))
    _alias(httpserver, CGIHTTPServer, (
        "CGIHTTPRequestHandler",
    ))

except ImportError:
    import urllib.request
    _alias(urlreq, urllib.request, (
        "AbstractHTTPHandler",
        "addclosehook",
        "addinfourl",
        "BaseHandler",
        "build_opener",
        "FileHandler",
        "FTPHandler",
        "ftpwrapper",
        "HTTPHandler",
        "HTTPSHandler",
        "install_opener",
        "pathname2url",
        "HTTPBasicAuthHandler",
        "HTTPDigestAuthHandler",
        "HTTPPasswordMgrWithDefaultRealm",
        "ProxyHandler",
        "quote",
        "Request",
        "splitattr",
        "splitpasswd",
        "splitport",
        "splituser",
        "unquote",
        "url2pathname",
        "urlopen",
    ))
    import urllib.error
    _alias(urlerr, urllib.error, (
        "HTTPError",
        "URLError",
    ))
    import http.server
    _alias(httpserver, http.server, (
        "HTTPServer",
        "BaseHTTPRequestHandler",
        "SimpleHTTPRequestHandler",
        "CGIHTTPRequestHandler",
    ))

try:
    xrange
except NameError:
    import builtins
    builtins.xrange = range