ui: add a "config_default" method

This allow code to access the expected value for a config. This is useful in the
context of dynamic default value, and short term it will be useful to write
dynamically "correct" code.

Differential Revision: https://phab.mercurial-scm.org/D9759

mercurial/ui.py

@@ -1,2381 +1,2393 b''
 # ui.py - user interface bits for mercurial
 #
 # Copyright 2005-2007 Matt Mackall <[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.
 
 from __future__ import absolute_import
 
 import collections
 import contextlib
 import datetime
 import errno
 import getpass
 import inspect
 import os
 import re
 import signal
 import socket
 import subprocess
 import sys
 import traceback
 
 from .i18n import _
 from .node import hex
 from .pycompat import (
     getattr,
     open,
     setattr,
 )
 
 from . import (
     color,
     config,
     configitems,
     encoding,
     error,
     formatter,
     loggingutil,
     progress,
     pycompat,
     rcutil,
     scmutil,
     util,
 )
 from .utils import (
     dateutil,
     procutil,
     resourceutil,
     stringutil,
 )
 
 urlreq = util.urlreq
 
 # for use with str.translate(None, _keepalnum), to keep just alphanumerics
 _keepalnum = b''.join(
     c for c in map(pycompat.bytechr, range(256)) if not c.isalnum()
 )
 
 # The config knobs that will be altered (if unset) by ui.tweakdefaults.
 tweakrc = b"""
 [ui]
 # Gives detailed exit codes for input/user errors, config errors, etc.
 detailed-exit-code = True
 # The rollback command is dangerous. As a rule, don't use it.
 rollback = False
 # Make `hg status` report copy information
 statuscopies = yes
 # Prefer curses UIs when available. Revert to plain-text with `text`.
 interface = curses
 # Make compatible commands emit cwd-relative paths by default.
 relative-paths = yes
 
 [commands]
 # Grep working directory by default.
 grep.all-files = True
 # Refuse to perform an `hg update` that would cause a file content merge
 update.check = noconflict
 # Show conflicts information in `hg status`
 status.verbose = True
 # Make `hg resolve` with no action (like `-m`) fail instead of re-merging.
 resolve.explicit-re-merge = True
 
 [diff]
 git = 1
 showfunc = 1
 word-diff = 1
 """
 
 samplehgrcs = {
     b'user': b"""# example user config (see 'hg help config' for more info)
 [ui]
 # name and email, e.g.
 # username = Jane Doe <[e-mail]>
 username =
 
 # We recommend enabling tweakdefaults to get slight improvements to
 # the UI over time. Make sure to set HGPLAIN in the environment when
 # writing scripts!
 # tweakdefaults = True
 
 # uncomment to disable color in command output
 # (see 'hg help color' for details)
 # color = never
 
 # uncomment to disable command output pagination
 # (see 'hg help pager' for details)
 # paginate = never
 
 [extensions]
 # uncomment the lines below to enable some popular extensions
 # (see 'hg help extensions' for more info)
 #
 # histedit =
 # rebase =
 # uncommit =
 """,
     b'cloned': b"""# example repository config (see 'hg help config' for more info)
 [paths]
 default = %s
 
 # path aliases to other clones of this repo in URLs or filesystem paths
 # (see 'hg help config.paths' for more info)
 #
 # default:pushurl = ssh://[e-mail]/hg/jdoes-fork
 # my-fork         = ssh://[e-mail]/hg/jdoes-fork
 # my-clone        = /home/jdoe/jdoes-clone
 
 [ui]
 # name and email (local to this repository, optional), e.g.
 # username = Jane Doe <[e-mail]>
 """,
     b'local': b"""# example repository config (see 'hg help config' for more info)
 [paths]
 # path aliases to other clones of this repo in URLs or filesystem paths
 # (see 'hg help config.paths' for more info)
 #
 # default         = http://example.com/hg/example-repo
 # default:pushurl = ssh://[e-mail]/hg/jdoes-fork
 # my-fork         = ssh://[e-mail]/hg/jdoes-fork
 # my-clone        = /home/jdoe/jdoes-clone
 
 [ui]
 # name and email (local to this repository, optional), e.g.
 # username = Jane Doe <[e-mail]>
 """,
     b'global': b"""# example system-wide hg config (see 'hg help config' for more info)
 
 [ui]
 # uncomment to disable color in command output
 # (see 'hg help color' for details)
 # color = never
 
 # uncomment to disable command output pagination
 # (see 'hg help pager' for details)
 # paginate = never
 
 [extensions]
 # uncomment the lines below to enable some popular extensions
 # (see 'hg help extensions' for more info)
 #
 # blackbox =
 # churn =
 """,
 }
 
 
 def _maybestrurl(maybebytes):
     return pycompat.rapply(pycompat.strurl, maybebytes)
 
 
 def _maybebytesurl(maybestr):
     return pycompat.rapply(pycompat.bytesurl, maybestr)
 
 
 class httppasswordmgrdbproxy(object):
     """Delays loading urllib2 until it's needed."""
 
     def __init__(self):
         self._mgr = None
 
     def _get_mgr(self):
         if self._mgr is None:
             self._mgr = urlreq.httppasswordmgrwithdefaultrealm()
         return self._mgr
 
     def add_password(self, realm, uris, user, passwd):
         return self._get_mgr().add_password(
             _maybestrurl(realm),
             _maybestrurl(uris),
             _maybestrurl(user),
             _maybestrurl(passwd),
         )
 
     def find_user_password(self, realm, uri):
         mgr = self._get_mgr()
         return _maybebytesurl(
             mgr.find_user_password(_maybestrurl(realm), _maybestrurl(uri))
         )
 
 
 def _catchterm(*args):
     raise error.SignalInterrupt
 
 
 # unique object used to detect no default value has been provided when
 # retrieving configuration value.
 _unset = object()
 
 # _reqexithandlers: callbacks run at the end of a request
 _reqexithandlers = []
 
 
 class ui(object):
     def __init__(self, src=None):
         """Create a fresh new ui object if no src given
 
         Use uimod.ui.load() to create a ui which knows global and user configs.
         In most cases, you should use ui.copy() to create a copy of an existing
         ui object.
         """
         # _buffers: used for temporary capture of output
         self._buffers = []
         # 3-tuple describing how each buffer in the stack behaves.
         # Values are (capture stderr, capture subprocesses, apply labels).
         self._bufferstates = []
         # When a buffer is active, defines whether we are expanding labels.
         # This exists to prevent an extra list lookup.
         self._bufferapplylabels = None
         self.quiet = self.verbose = self.debugflag = self.tracebackflag = False
         self._reportuntrusted = True
         self._knownconfig = configitems.coreitems
         self._ocfg = config.config()  # overlay
         self._tcfg = config.config()  # trusted
         self._ucfg = config.config()  # untrusted
         self._trustusers = set()
         self._trustgroups = set()
         self.callhooks = True
         # Insecure server connections requested.
         self.insecureconnections = False
         # Blocked time
         self.logblockedtimes = False
         # color mode: see mercurial/color.py for possible value
         self._colormode = None
         self._terminfoparams = {}
         self._styles = {}
         self._uninterruptible = False
         self.showtimestamp = False
 
         if src:
             self._fout = src._fout
             self._ferr = src._ferr
             self._fin = src._fin
             self._fmsg = src._fmsg
             self._fmsgout = src._fmsgout
             self._fmsgerr = src._fmsgerr
             self._finoutredirected = src._finoutredirected
             self._loggers = src._loggers.copy()
             self.pageractive = src.pageractive
             self._disablepager = src._disablepager
             self._tweaked = src._tweaked
 
             self._tcfg = src._tcfg.copy()
             self._ucfg = src._ucfg.copy()
             self._ocfg = src._ocfg.copy()
             self._trustusers = src._trustusers.copy()
             self._trustgroups = src._trustgroups.copy()
             self.environ = src.environ
             self.callhooks = src.callhooks
             self.insecureconnections = src.insecureconnections
             self._colormode = src._colormode
             self._terminfoparams = src._terminfoparams.copy()
             self._styles = src._styles.copy()
 
             self.fixconfig()
 
             self.httppasswordmgrdb = src.httppasswordmgrdb
             self._blockedtimes = src._blockedtimes
         else:
             self._fout = procutil.stdout
             self._ferr = procutil.stderr
             self._fin = procutil.stdin
             self._fmsg = None
             self._fmsgout = self.fout  # configurable
             self._fmsgerr = self.ferr  # configurable
             self._finoutredirected = False
             self._loggers = {}
             self.pageractive = False
             self._disablepager = False
             self._tweaked = False
 
             # shared read-only environment
             self.environ = encoding.environ
 
             self.httppasswordmgrdb = httppasswordmgrdbproxy()
             self._blockedtimes = collections.defaultdict(int)
 
         allowed = self.configlist(b'experimental', b'exportableenviron')
         if b'*' in allowed:
             self._exportableenviron = self.environ
         else:
             self._exportableenviron = {}
             for k in allowed:
                 if k in self.environ:
                     self._exportableenviron[k] = self.environ[k]
 
     @classmethod
     def load(cls):
         """Create a ui and load global and user configs"""
         u = cls()
         # we always trust global config files and environment variables
         for t, f in rcutil.rccomponents():
             if t == b'path':
                 u.readconfig(f, trust=True)
             elif t == b'resource':
                 u.read_resource_config(f, trust=True)
             elif t == b'items':
                 sections = set()
                 for section, name, value, source in f:
                     # do not set u._ocfg
                     # XXX clean this up once immutable config object is a thing
                     u._tcfg.set(section, name, value, source)
                     u._ucfg.set(section, name, value, source)
                     sections.add(section)
                 for section in sections:
                     u.fixconfig(section=section)
             else:
                 raise error.ProgrammingError(b'unknown rctype: %s' % t)
         u._maybetweakdefaults()
         return u
 
     def _maybetweakdefaults(self):
         if not self.configbool(b'ui', b'tweakdefaults'):
             return
         if self._tweaked or self.plain(b'tweakdefaults'):
             return
 
         # Note: it is SUPER IMPORTANT that you set self._tweaked to
         # True *before* any calls to setconfig(), otherwise you'll get
         # infinite recursion between setconfig and this method.
         #
         # TODO: We should extract an inner method in setconfig() to
         # avoid this weirdness.
         self._tweaked = True
         tmpcfg = config.config()
         tmpcfg.parse(b'<tweakdefaults>', tweakrc)
         for section in tmpcfg:
             for name, value in tmpcfg.items(section):
                 if not self.hasconfig(section, name):
                     self.setconfig(section, name, value, b"<tweakdefaults>")
 
     def copy(self):
         return self.__class__(self)
 
     def resetstate(self):
         """Clear internal state that shouldn't persist across commands"""
         if self._progbar:
             self._progbar.resetstate()  # reset last-print time of progress bar
         self.httppasswordmgrdb = httppasswordmgrdbproxy()
 
     @contextlib.contextmanager
     def timeblockedsection(self, key):
         # this is open-coded below - search for timeblockedsection to find them
         starttime = util.timer()
         try:
             yield
         finally:
             self._blockedtimes[key + b'_blocked'] += (
                 util.timer() - starttime
             ) * 1000
 
     @contextlib.contextmanager
     def uninterruptible(self):
         """Mark an operation as unsafe.
 
         Most operations on a repository are safe to interrupt, but a
         few are risky (for example repair.strip). This context manager
         lets you advise Mercurial that something risky is happening so
         that control-C etc can be blocked if desired.
         """
         enabled = self.configbool(b'experimental', b'nointerrupt')
         if enabled and self.configbool(
             b'experimental', b'nointerrupt-interactiveonly'
         ):
             enabled = self.interactive()
         if self._uninterruptible or not enabled:
             # if nointerrupt support is turned off, the process isn't
             # interactive, or we're already in an uninterruptible
             # block, do nothing.
             yield
             return
 
         def warn():
             self.warn(_(b"shutting down cleanly\n"))
             self.warn(
                 _(b"press ^C again to terminate immediately (dangerous)\n")
             )
             return True
 
         with procutil.uninterruptible(warn):
             try:
                 self._uninterruptible = True
                 yield
             finally:
                 self._uninterruptible = False
 
     def formatter(self, topic, opts):
         return formatter.formatter(self, self, topic, opts)
 
     def _trusted(self, fp, f):
         st = util.fstat(fp)
         if util.isowner(st):
             return True
 
         tusers, tgroups = self._trustusers, self._trustgroups
         if b'*' in tusers or b'*' in tgroups:
             return True
 
         user = util.username(st.st_uid)
         group = util.groupname(st.st_gid)
         if user in tusers or group in tgroups or user == util.username():
             return True
 
         if self._reportuntrusted:
             self.warn(
                 _(
                     b'not trusting file %s from untrusted '
                     b'user %s, group %s\n'
                 )
                 % (f, user, group)
             )
         return False
 
     def read_resource_config(
         self, name, root=None, trust=False, sections=None, remap=None
     ):
         try:
             fp = resourceutil.open_resource(name[0], name[1])
         except IOError:
             if not sections:  # ignore unless we were looking for something
                 return
             raise
 
         self._readconfig(
             b'resource:%s.%s' % name, fp, root, trust, sections, remap
         )
 
     def readconfig(
         self, filename, root=None, trust=False, sections=None, remap=None
     ):
         try:
             fp = open(filename, 'rb')
         except IOError:
             if not sections:  # ignore unless we were looking for something
                 return
             raise
 
         self._readconfig(filename, fp, root, trust, sections, remap)
 
     def _readconfig(
         self, filename, fp, root=None, trust=False, sections=None, remap=None
     ):
         with fp:
             cfg = config.config()
             trusted = sections or trust or self._trusted(fp, filename)
 
             try:
                 cfg.read(filename, fp, sections=sections, remap=remap)
             except error.ConfigError as inst:
                 if trusted:
                     raise
                 self.warn(
                     _(b'ignored %s: %s\n') % (inst.location, inst.message)
                 )
 
         self._applyconfig(cfg, trusted, root)
 
     def applyconfig(self, configitems, source=b"", root=None):
         """Add configitems from a non-file source.  Unlike with ``setconfig()``,
         they can be overridden by subsequent config file reads.  The items are
         in the same format as ``configoverride()``, namely a dict of the
         following structures: {(section, name) : value}
 
         Typically this is used by extensions that inject themselves into the
         config file load procedure by monkeypatching ``localrepo.loadhgrc()``.
         """
         cfg = config.config()
 
         for (section, name), value in configitems.items():
             cfg.set(section, name, value, source)
 
         self._applyconfig(cfg, True, root)
 
     def _applyconfig(self, cfg, trusted, root):
         if self.plain():
             for k in (
                 b'debug',
                 b'fallbackencoding',
                 b'quiet',
                 b'slash',
                 b'logtemplate',
                 b'message-output',
                 b'statuscopies',
                 b'style',
                 b'traceback',
                 b'verbose',
             ):
                 if k in cfg[b'ui']:
                     del cfg[b'ui'][k]
             for k, v in cfg.items(b'defaults'):
                 del cfg[b'defaults'][k]
             for k, v in cfg.items(b'commands'):
                 del cfg[b'commands'][k]
             for k, v in cfg.items(b'command-templates'):
                 del cfg[b'command-templates'][k]
         # Don't remove aliases from the configuration if in the exceptionlist
         if self.plain(b'alias'):
             for k, v in cfg.items(b'alias'):
                 del cfg[b'alias'][k]
         if self.plain(b'revsetalias'):
             for k, v in cfg.items(b'revsetalias'):
                 del cfg[b'revsetalias'][k]
         if self.plain(b'templatealias'):
             for k, v in cfg.items(b'templatealias'):
                 del cfg[b'templatealias'][k]
 
         if trusted:
             self._tcfg.update(cfg)
             self._tcfg.update(self._ocfg)
         self._ucfg.update(cfg)
         self._ucfg.update(self._ocfg)
 
         if root is None:
             root = os.path.expanduser(b'~')
         self.fixconfig(root=root)
 
     def fixconfig(self, root=None, section=None):
         if section in (None, b'paths'):
             # expand vars and ~
             # translate paths relative to root (or home) into absolute paths
             root = root or encoding.getcwd()
             for c in self._tcfg, self._ucfg, self._ocfg:
                 for n, p in c.items(b'paths'):
                     # Ignore sub-options.
                     if b':' in n:
                         continue
                     if not p:
                         continue
                     if b'%%' in p:
                         s = self.configsource(b'paths', n) or b'none'
                         self.warn(
                             _(b"(deprecated '%%' in path %s=%s from %s)\n")
                             % (n, p, s)
                         )
                         p = p.replace(b'%%', b'%')
                     p = util.expandpath(p)
                     if not util.hasscheme(p) and not os.path.isabs(p):
                         p = os.path.normpath(os.path.join(root, p))
                     c.set(b"paths", n, p)
 
         if section in (None, b'ui'):
             # update ui options
             self._fmsgout, self._fmsgerr = _selectmsgdests(self)
             self.debugflag = self.configbool(b'ui', b'debug')
             self.verbose = self.debugflag or self.configbool(b'ui', b'verbose')
             self.quiet = not self.debugflag and self.configbool(b'ui', b'quiet')
             if self.verbose and self.quiet:
                 self.quiet = self.verbose = False
             self._reportuntrusted = self.debugflag or self.configbool(
                 b"ui", b"report_untrusted"
             )
             self.showtimestamp = self.configbool(b'ui', b'timestamp-output')
             self.tracebackflag = self.configbool(b'ui', b'traceback')
             self.logblockedtimes = self.configbool(b'ui', b'logblockedtimes')
 
         if section in (None, b'trusted'):
             # update trust information
             self._trustusers.update(self.configlist(b'trusted', b'users'))
             self._trustgroups.update(self.configlist(b'trusted', b'groups'))
 
         if section in (None, b'devel', b'ui') and self.debugflag:
             tracked = set()
             if self.configbool(b'devel', b'debug.extensions'):
                 tracked.add(b'extension')
             if tracked:
                 logger = loggingutil.fileobjectlogger(self._ferr, tracked)
                 self.setlogger(b'debug', logger)
 
     def backupconfig(self, section, item):
         return (
             self._ocfg.backup(section, item),
             self._tcfg.backup(section, item),
             self._ucfg.backup(section, item),
         )
 
     def restoreconfig(self, data):
         self._ocfg.restore(data[0])
         self._tcfg.restore(data[1])
         self._ucfg.restore(data[2])
 
     def setconfig(self, section, name, value, source=b''):
         for cfg in (self._ocfg, self._tcfg, self._ucfg):
             cfg.set(section, name, value, source)
         self.fixconfig(section=section)
         self._maybetweakdefaults()
 
     def _data(self, untrusted):
         return untrusted and self._ucfg or self._tcfg
 
     def configsource(self, section, name, untrusted=False):
         return self._data(untrusted).source(section, name)
 
     def config(self, section, name, default=_unset, untrusted=False):
         """return the plain string version of a config"""
         value = self._config(
             section, name, default=default, untrusted=untrusted
         )
         if value is _unset:
             return None
         return value
 
     def _config(self, section, name, default=_unset, untrusted=False):
         value = itemdefault = default
         item = self._knownconfig.get(section, {}).get(name)
         alternates = [(section, name)]
 
         if item is not None:
             alternates.extend(item.alias)
             if callable(item.default):
                 itemdefault = item.default()
             else:
                 itemdefault = item.default
         else:
             msg = b"accessing unregistered config item: '%s.%s'"
             msg %= (section, name)
             self.develwarn(msg, 2, b'warn-config-unknown')
 
         if default is _unset:
             if item is None:
                 value = default
             elif item.default is configitems.dynamicdefault:
                 value = None
                 msg = b"config item requires an explicit default value: '%s.%s'"
                 msg %= (section, name)
                 self.develwarn(msg, 2, b'warn-config-default')
             else:
                 value = itemdefault
         elif (
             item is not None
             and item.default is not configitems.dynamicdefault
             and default != itemdefault
         ):
             msg = (
                 b"specifying a mismatched default value for a registered "
                 b"config item: '%s.%s' '%s'"
             )
             msg %= (section, name, pycompat.bytestr(default))
             self.develwarn(msg, 2, b'warn-config-default')
 
         for s, n in alternates:
             candidate = self._data(untrusted).get(s, n, None)
             if candidate is not None:
                 value = candidate
                 break
 
         if self.debugflag and not untrusted and self._reportuntrusted:
             for s, n in alternates:
                 uvalue = self._ucfg.get(s, n)
                 if uvalue is not None and uvalue != value:
                     self.debug(
                         b"ignoring untrusted configuration option "
                         b"%s.%s = %s\n" % (s, n, uvalue)
                     )
         return value
 
+    def config_default(self, section, name):
+        """return the default value for a config option
+
+        The default is returned "raw", for example if it is a callable, the
+        callable was not called.
+        """
+        item = self._knownconfig.get(section, {}).get(name)
+
+        if item is None:
+            raise KeyError((section, name))
+        return item.default
+
     def configsuboptions(self, section, name, default=_unset, untrusted=False):
         """Get a config option and all sub-options.
 
         Some config options have sub-options that are declared with the
         format "key:opt = value". This method is used to return the main
         option and all its declared sub-options.
 
         Returns a 2-tuple of ``(option, sub-options)``, where `sub-options``
         is a dict of defined sub-options where keys and values are strings.
         """
         main = self.config(section, name, default, untrusted=untrusted)
         data = self._data(untrusted)
         sub = {}
         prefix = b'%s:' % name
         for k, v in data.items(section):
             if k.startswith(prefix):
                 sub[k[len(prefix) :]] = v
 
         if self.debugflag and not untrusted and self._reportuntrusted:
             for k, v in sub.items():
                 uvalue = self._ucfg.get(section, b'%s:%s' % (name, k))
                 if uvalue is not None and uvalue != v:
                     self.debug(
                         b'ignoring untrusted configuration option '
                         b'%s:%s.%s = %s\n' % (section, name, k, uvalue)
                     )
 
         return main, sub
 
     def configpath(self, section, name, default=_unset, untrusted=False):
         """get a path config item, expanded relative to repo root or config
         file"""
         v = self.config(section, name, default, untrusted)
         if v is None:
             return None
         if not os.path.isabs(v) or b"://" not in v:
             src = self.configsource(section, name, untrusted)
             if b':' in src:
                 base = os.path.dirname(src.rsplit(b':')[0])
                 v = os.path.join(base, os.path.expanduser(v))
         return v
 
     def configbool(self, section, name, default=_unset, untrusted=False):
         """parse a configuration element as a boolean
 
         >>> u = ui(); s = b'foo'
         >>> u.setconfig(s, b'true', b'yes')
         >>> u.configbool(s, b'true')
         True
         >>> u.setconfig(s, b'false', b'no')
         >>> u.configbool(s, b'false')
         False
         >>> u.configbool(s, b'unknown')
         False
         >>> u.configbool(s, b'unknown', True)
         True
         >>> u.setconfig(s, b'invalid', b'somevalue')
         >>> u.configbool(s, b'invalid')
         Traceback (most recent call last):
             ...
         ConfigError: foo.invalid is not a boolean ('somevalue')
         """
 
         v = self._config(section, name, default, untrusted=untrusted)
         if v is None:
             return v
         if v is _unset:
             if default is _unset:
                 return False
             return default
         if isinstance(v, bool):
             return v
         b = stringutil.parsebool(v)
         if b is None:
             raise error.ConfigError(
                 _(b"%s.%s is not a boolean ('%s')") % (section, name, v)
             )
         return b
 
     def configwith(
         self, convert, section, name, default=_unset, desc=None, untrusted=False
     ):
         """parse a configuration element with a conversion function
 
         >>> u = ui(); s = b'foo'
         >>> u.setconfig(s, b'float1', b'42')
         >>> u.configwith(float, s, b'float1')
         42.0
         >>> u.setconfig(s, b'float2', b'-4.25')
         >>> u.configwith(float, s, b'float2')
         -4.25
         >>> u.configwith(float, s, b'unknown', 7)
         7.0
         >>> u.setconfig(s, b'invalid', b'somevalue')
         >>> u.configwith(float, s, b'invalid')
         Traceback (most recent call last):
             ...
         ConfigError: foo.invalid is not a valid float ('somevalue')
         >>> u.configwith(float, s, b'invalid', desc=b'womble')
         Traceback (most recent call last):
             ...
         ConfigError: foo.invalid is not a valid womble ('somevalue')
         """
 
         v = self.config(section, name, default, untrusted)
         if v is None:
             return v  # do not attempt to convert None
         try:
             return convert(v)
         except (ValueError, error.ParseError):
             if desc is None:
                 desc = pycompat.sysbytes(convert.__name__)
             raise error.ConfigError(
                 _(b"%s.%s is not a valid %s ('%s')") % (section, name, desc, v)
             )
 
     def configint(self, section, name, default=_unset, untrusted=False):
         """parse a configuration element as an integer
 
         >>> u = ui(); s = b'foo'
         >>> u.setconfig(s, b'int1', b'42')
         >>> u.configint(s, b'int1')
         42
         >>> u.setconfig(s, b'int2', b'-42')
         >>> u.configint(s, b'int2')
         -42
         >>> u.configint(s, b'unknown', 7)
         7
         >>> u.setconfig(s, b'invalid', b'somevalue')
         >>> u.configint(s, b'invalid')
         Traceback (most recent call last):
             ...
         ConfigError: foo.invalid is not a valid integer ('somevalue')
         """
 
         return self.configwith(
             int, section, name, default, b'integer', untrusted
         )
 
     def configbytes(self, section, name, default=_unset, untrusted=False):
         """parse a configuration element as a quantity in bytes
 
         Units can be specified as b (bytes), k or kb (kilobytes), m or
         mb (megabytes), g or gb (gigabytes).
 
         >>> u = ui(); s = b'foo'
         >>> u.setconfig(s, b'val1', b'42')
         >>> u.configbytes(s, b'val1')
         42
         >>> u.setconfig(s, b'val2', b'42.5 kb')
         >>> u.configbytes(s, b'val2')
         43520
         >>> u.configbytes(s, b'unknown', b'7 MB')
         7340032
         >>> u.setconfig(s, b'invalid', b'somevalue')
         >>> u.configbytes(s, b'invalid')
         Traceback (most recent call last):
             ...
         ConfigError: foo.invalid is not a byte quantity ('somevalue')
         """
 
         value = self._config(section, name, default, untrusted)
         if value is _unset:
             if default is _unset:
                 default = 0
             value = default
         if not isinstance(value, bytes):
             return value
         try:
             return util.sizetoint(value)
         except error.ParseError:
             raise error.ConfigError(
                 _(b"%s.%s is not a byte quantity ('%s')")
                 % (section, name, value)
             )
 
     def configlist(self, section, name, default=_unset, untrusted=False):
         """parse a configuration element as a list of comma/space separated
         strings
 
         >>> u = ui(); s = b'foo'
         >>> u.setconfig(s, b'list1', b'this,is "a small" ,test')
         >>> u.configlist(s, b'list1')
         ['this', 'is', 'a small', 'test']
         >>> u.setconfig(s, b'list2', b'this, is "a small" , test ')
         >>> u.configlist(s, b'list2')
         ['this', 'is', 'a small', 'test']
         """
         # default is not always a list
         v = self.configwith(
             config.parselist, section, name, default, b'list', untrusted
         )
         if isinstance(v, bytes):
             return config.parselist(v)
         elif v is None:
             return []
         return v
 
     def configdate(self, section, name, default=_unset, untrusted=False):
         """parse a configuration element as a tuple of ints
 
         >>> u = ui(); s = b'foo'
         >>> u.setconfig(s, b'date', b'0 0')
         >>> u.configdate(s, b'date')
         (0, 0)
         """
         if self.config(section, name, default, untrusted):
             return self.configwith(
                 dateutil.parsedate, section, name, default, b'date', untrusted
             )
         if default is _unset:
             return None
         return default
 
     def configdefault(self, section, name):
         """returns the default value of the config item"""
         item = self._knownconfig.get(section, {}).get(name)
         itemdefault = None
         if item is not None:
             if callable(item.default):
                 itemdefault = item.default()
             else:
                 itemdefault = item.default
         return itemdefault
 
     def hasconfig(self, section, name, untrusted=False):
         return self._data(untrusted).hasitem(section, name)
 
     def has_section(self, section, untrusted=False):
         '''tell whether section exists in config.'''
         return section in self._data(untrusted)
 
     def configitems(self, section, untrusted=False, ignoresub=False):
         items = self._data(untrusted).items(section)
         if ignoresub:
             items = [i for i in items if b':' not in i[0]]
         if self.debugflag and not untrusted and self._reportuntrusted:
             for k, v in self._ucfg.items(section):
                 if self._tcfg.get(section, k) != v:
                     self.debug(
                         b"ignoring untrusted configuration option "
                         b"%s.%s = %s\n" % (section, k, v)
                     )
         return items
 
     def walkconfig(self, untrusted=False):
         cfg = self._data(untrusted)
         for section in cfg.sections():
             for name, value in self.configitems(section, untrusted):
                 yield section, name, value
 
     def plain(self, feature=None):
         """is plain mode active?
 
         Plain mode means that all configuration variables which affect
         the behavior and output of Mercurial should be
         ignored. Additionally, the output should be stable,
         reproducible and suitable for use in scripts or applications.
 
         The only way to trigger plain mode is by setting either the
         `HGPLAIN' or `HGPLAINEXCEPT' environment variables.
 
         The return value can either be
         - False if HGPLAIN is not set, or feature is in HGPLAINEXCEPT
         - False if feature is disabled by default and not included in HGPLAIN
         - True otherwise
         """
         if (
             b'HGPLAIN' not in encoding.environ
             and b'HGPLAINEXCEPT' not in encoding.environ
         ):
             return False
         exceptions = (
             encoding.environ.get(b'HGPLAINEXCEPT', b'').strip().split(b',')
         )
         # TODO: add support for HGPLAIN=+feature,-feature syntax
         if b'+strictflags' not in encoding.environ.get(b'HGPLAIN', b'').split(
             b','
         ):
             exceptions.append(b'strictflags')
         if feature and exceptions:
             return feature not in exceptions
         return True
 
     def username(self, acceptempty=False):
         """Return default username to be used in commits.
 
         Searched in this order: $HGUSER, [ui] section of hgrcs, $EMAIL
         and stop searching if one of these is set.
         If not found and acceptempty is True, returns None.
         If not found and ui.askusername is True, ask the user, else use
         ($LOGNAME or $USER or $LNAME or $USERNAME) + "@full.hostname".
         If no username could be found, raise an Abort error.
         """
         user = encoding.environ.get(b"HGUSER")
         if user is None:
             user = self.config(b"ui", b"username")
             if user is not None:
                 user = os.path.expandvars(user)
         if user is None:
             user = encoding.environ.get(b"EMAIL")
         if user is None and acceptempty:
             return user
         if user is None and self.configbool(b"ui", b"askusername"):
             user = self.prompt(_(b"enter a commit username:"), default=None)
         if user is None and not self.interactive():
             try:
                 user = b'%s@%s' % (
                     procutil.getuser(),
                     encoding.strtolocal(socket.getfqdn()),
                 )
                 self.warn(_(b"no username found, using '%s' instead\n") % user)
             except KeyError:
                 pass
         if not user:
             raise error.Abort(
                 _(b'no username supplied'),
                 hint=_(b"use 'hg config --edit' " b'to set your username'),
             )
         if b"\n" in user:
             raise error.Abort(
                 _(b"username %r contains a newline\n") % pycompat.bytestr(user)
             )
         return user
 
     def shortuser(self, user):
         """Return a short representation of a user name or email address."""
         if not self.verbose:
             user = stringutil.shortuser(user)
         return user
 
     def expandpath(self, loc, default=None):
         """Return repository location relative to cwd or from [paths]"""
         try:
             p = self.paths.getpath(loc)
             if p:
                 return p.rawloc
         except error.RepoError:
             pass
 
         if default:
             try:
                 p = self.paths.getpath(default)
                 if p:
                     return p.rawloc
             except error.RepoError:
                 pass
 
         return loc
 
     @util.propertycache
     def paths(self):
         return paths(self)
 
     @property
     def fout(self):
         return self._fout
 
     @fout.setter
     def fout(self, f):
         self._fout = f
         self._fmsgout, self._fmsgerr = _selectmsgdests(self)
 
     @property
     def ferr(self):
         return self._ferr
 
     @ferr.setter
     def ferr(self, f):
         self._ferr = f
         self._fmsgout, self._fmsgerr = _selectmsgdests(self)
 
     @property
     def fin(self):
         return self._fin
 
     @fin.setter
     def fin(self, f):
         self._fin = f
 
     @property
     def fmsg(self):
         """Stream dedicated for status/error messages; may be None if
         fout/ferr are used"""
         return self._fmsg
 
     @fmsg.setter
     def fmsg(self, f):
         self._fmsg = f
         self._fmsgout, self._fmsgerr = _selectmsgdests(self)
 
     def pushbuffer(self, error=False, subproc=False, labeled=False):
         """install a buffer to capture standard output of the ui object
 
         If error is True, the error output will be captured too.
 
         If subproc is True, output from subprocesses (typically hooks) will be
         captured too.
 
         If labeled is True, any labels associated with buffered
         output will be handled. By default, this has no effect
         on the output returned, but extensions and GUI tools may
         handle this argument and returned styled output. If output
         is being buffered so it can be captured and parsed or
         processed, labeled should not be set to True.
         """
         self._buffers.append([])
         self._bufferstates.append((error, subproc, labeled))
         self._bufferapplylabels = labeled
 
     def popbuffer(self):
         '''pop the last buffer and return the buffered output'''
         self._bufferstates.pop()
         if self._bufferstates:
             self._bufferapplylabels = self._bufferstates[-1][2]
         else:
             self._bufferapplylabels = None
 
         return b"".join(self._buffers.pop())
 
     def _isbuffered(self, dest):
         if dest is self._fout:
             return bool(self._buffers)
         if dest is self._ferr:
             return bool(self._bufferstates and self._bufferstates[-1][0])
         return False
 
     def canwritewithoutlabels(self):
         '''check if write skips the label'''
         if self._buffers and not self._bufferapplylabels:
             return True
         return self._colormode is None
 
     def canbatchlabeledwrites(self):
         '''check if write calls with labels are batchable'''
         # Windows color printing is special, see ``write``.
         return self._colormode != b'win32'
 
     def write(self, *args, **opts):
         """write args to output
 
         By default, this method simply writes to the buffer or stdout.
         Color mode can be set on the UI class to have the output decorated
         with color modifier before being written to stdout.
 
         The color used is controlled by an optional keyword argument, "label".
         This should be a string containing label names separated by space.
         Label names take the form of "topic.type". For example, ui.debug()
         issues a label of "ui.debug".
 
         Progress reports via stderr are normally cleared before writing as
         stdout and stderr go to the same terminal. This can be skipped with
         the optional keyword argument "keepprogressbar". The progress bar
         will continue to occupy a partial line on stderr in that case.
         This functionality is intended when Mercurial acts as data source
         in a pipe.
 
         When labeling output for a specific command, a label of
         "cmdname.type" is recommended. For example, status issues
         a label of "status.modified" for modified files.
         """
         dest = self._fout
 
         # inlined _write() for speed
         if self._buffers:
             label = opts.get('label', b'')
             if label and self._bufferapplylabels:
                 self._buffers[-1].extend(self.label(a, label) for a in args)
             else:
                 self._buffers[-1].extend(args)
             return
 
         # inlined _writenobuf() for speed
         if not opts.get('keepprogressbar', False):
             self._progclear()
         msg = b''.join(args)
 
         # opencode timeblockedsection because this is a critical path
         starttime = util.timer()
         try:
             if self._colormode == b'win32':
                 # windows color printing is its own can of crab, defer to
                 # the color module and that is it.
                 color.win32print(self, dest.write, msg, **opts)
             else:
                 if self._colormode is not None:
                     label = opts.get('label', b'')
                     msg = self.label(msg, label)
                 dest.write(msg)
         except IOError as err:
             raise error.StdioError(err)
         finally:
             self._blockedtimes[b'stdio_blocked'] += (
                 util.timer() - starttime
             ) * 1000
 
     def write_err(self, *args, **opts):
         self._write(self._ferr, *args, **opts)
 
     def _write(self, dest, *args, **opts):
         # update write() as well if you touch this code
         if self._isbuffered(dest):
             label = opts.get('label', b'')
             if label and self._bufferapplylabels:
                 self._buffers[-1].extend(self.label(a, label) for a in args)
             else:
                 self._buffers[-1].extend(args)
         else:
             self._writenobuf(dest, *args, **opts)
 
     def _writenobuf(self, dest, *args, **opts):
         # update write() as well if you touch this code
         if not opts.get('keepprogressbar', False):
             self._progclear()
         msg = b''.join(args)
 
         # opencode timeblockedsection because this is a critical path
         starttime = util.timer()
         try:
             if dest is self._ferr and not getattr(self._fout, 'closed', False):
                 self._fout.flush()
             if getattr(dest, 'structured', False):
                 # channel for machine-readable output with metadata, where
                 # no extra colorization is necessary.
                 dest.write(msg, **opts)
             elif self._colormode == b'win32':
                 # windows color printing is its own can of crab, defer to
                 # the color module and that is it.
                 color.win32print(self, dest.write, msg, **opts)
             else:
                 if self._colormode is not None:
                     label = opts.get('label', b'')
                     msg = self.label(msg, label)
                 dest.write(msg)
             # stderr may be buffered under win32 when redirected to files,
             # including stdout.
             if dest is self._ferr and not getattr(dest, 'closed', False):
                 dest.flush()
         except IOError as err:
             if dest is self._ferr and err.errno in (
                 errno.EPIPE,
                 errno.EIO,
                 errno.EBADF,
             ):
                 # no way to report the error, so ignore it
                 return
             raise error.StdioError(err)
         finally:
             self._blockedtimes[b'stdio_blocked'] += (
                 util.timer() - starttime
             ) * 1000
 
     def _writemsg(self, dest, *args, **opts):
         timestamp = self.showtimestamp and opts.get('type') in {
             b'debug',
             b'error',
             b'note',
             b'status',
             b'warning',
         }
         if timestamp:
             args = (
                 b'[%s] '
                 % pycompat.bytestr(datetime.datetime.now().isoformat()),
             ) + args
         _writemsgwith(self._write, dest, *args, **opts)
         if timestamp:
             dest.flush()
 
     def _writemsgnobuf(self, dest, *args, **opts):
         _writemsgwith(self._writenobuf, dest, *args, **opts)
 
     def flush(self):
         # opencode timeblockedsection because this is a critical path
         starttime = util.timer()
         try:
             try:
                 self._fout.flush()
             except IOError as err:
                 if err.errno not in (errno.EPIPE, errno.EIO, errno.EBADF):
                     raise error.StdioError(err)
             finally:
                 try:
                     self._ferr.flush()
                 except IOError as err:
                     if err.errno not in (errno.EPIPE, errno.EIO, errno.EBADF):
                         raise error.StdioError(err)
         finally:
             self._blockedtimes[b'stdio_blocked'] += (
                 util.timer() - starttime
             ) * 1000
 
     def _isatty(self, fh):
         if self.configbool(b'ui', b'nontty'):
             return False
         return procutil.isatty(fh)
 
     def protectfinout(self):
         """Duplicate ui streams and redirect original if they are stdio
 
         Returns (fin, fout) which point to the original ui fds, but may be
         copy of them. The returned streams can be considered "owned" in that
         print(), exec(), etc. never reach to them.
         """
         if self._finoutredirected:
             # if already redirected, protectstdio() would just create another
             # nullfd pair, which is equivalent to returning self._fin/_fout.
             return self._fin, self._fout
         fin, fout = procutil.protectstdio(self._fin, self._fout)
         self._finoutredirected = (fin, fout) != (self._fin, self._fout)
         return fin, fout
 
     def restorefinout(self, fin, fout):
         """Restore ui streams from possibly duplicated (fin, fout)"""
         if (fin, fout) == (self._fin, self._fout):
             return
         procutil.restorestdio(self._fin, self._fout, fin, fout)
         # protectfinout() won't create more than one duplicated streams,
         # so we can just turn the redirection flag off.
         self._finoutredirected = False
 
     @contextlib.contextmanager
     def protectedfinout(self):
         """Run code block with protected standard streams"""
         fin, fout = self.protectfinout()
         try:
             yield fin, fout
         finally:
             self.restorefinout(fin, fout)
 
     def disablepager(self):
         self._disablepager = True
 
     def pager(self, command):
         """Start a pager for subsequent command output.
 
         Commands which produce a long stream of output should call
         this function to activate the user's preferred pagination
         mechanism (which may be no pager). Calling this function
         precludes any future use of interactive functionality, such as
         prompting the user or activating curses.
 
         Args:
           command: The full, non-aliased name of the command. That is, "log"
                    not "history, "summary" not "summ", etc.
         """
         if self._disablepager or self.pageractive:
             # how pager should do is already determined
             return
 
         if not command.startswith(b'internal-always-') and (
             # explicit --pager=on (= 'internal-always-' prefix) should
             # take precedence over disabling factors below
             command in self.configlist(b'pager', b'ignore')
             or not self.configbool(b'ui', b'paginate')
             or not self.configbool(b'pager', b'attend-' + command, True)
             or encoding.environ.get(b'TERM') == b'dumb'
             # TODO: if we want to allow HGPLAINEXCEPT=pager,
             # formatted() will need some adjustment.
             or not self.formatted()
             or self.plain()
             or self._buffers
             # TODO: expose debugger-enabled on the UI object
             or b'--debugger' in pycompat.sysargv
         ):
             # We only want to paginate if the ui appears to be
             # interactive, the user didn't say HGPLAIN or
             # HGPLAINEXCEPT=pager, and the user didn't specify --debug.
             return
 
         pagercmd = self.config(b'pager', b'pager', rcutil.fallbackpager)
         if not pagercmd:
             return
 
         pagerenv = {}
         for name, value in rcutil.defaultpagerenv().items():
             if name not in encoding.environ:
                 pagerenv[name] = value
 
         self.debug(
             b'starting pager for command %s\n' % stringutil.pprint(command)
         )
         self.flush()
 
         wasformatted = self.formatted()
         if util.safehasattr(signal, b"SIGPIPE"):
             signal.signal(signal.SIGPIPE, _catchterm)
         if self._runpager(pagercmd, pagerenv):
             self.pageractive = True
             # Preserve the formatted-ness of the UI. This is important
             # because we mess with stdout, which might confuse
             # auto-detection of things being formatted.
             self.setconfig(b'ui', b'formatted', wasformatted, b'pager')
             self.setconfig(b'ui', b'interactive', False, b'pager')
 
             # If pagermode differs from color.mode, reconfigure color now that
             # pageractive is set.
             cm = self._colormode
             if cm != self.config(b'color', b'pagermode', cm):
                 color.setup(self)
         else:
             # If the pager can't be spawned in dispatch when --pager=on is
             # given, don't try again when the command runs, to avoid a duplicate
             # warning about a missing pager command.
             self.disablepager()
 
     def _runpager(self, command, env=None):
         """Actually start the pager and set up file descriptors.
 
         This is separate in part so that extensions (like chg) can
         override how a pager is invoked.
         """
         if command == b'cat':
             # Save ourselves some work.
             return False
         # If the command doesn't contain any of these characters, we
         # assume it's a binary and exec it directly. This means for
         # simple pager command configurations, we can degrade
         # gracefully and tell the user about their broken pager.
         shell = any(c in command for c in b"|&;<>()$`\\\"' \t\n*?[#~=%")
 
         if pycompat.iswindows and not shell:
             # Window's built-in `more` cannot be invoked with shell=False, but
             # its `more.com` can.  Hide this implementation detail from the
             # user so we can also get sane bad PAGER behavior.  MSYS has
             # `more.exe`, so do a cmd.exe style resolution of the executable to
             # determine which one to use.
             fullcmd = procutil.findexe(command)
             if not fullcmd:
                 self.warn(
                     _(b"missing pager command '%s', skipping pager\n") % command
                 )
                 return False
 
             command = fullcmd
 
         try:
             pager = subprocess.Popen(
                 procutil.tonativestr(command),
                 shell=shell,
                 bufsize=-1,
                 close_fds=procutil.closefds,
                 stdin=subprocess.PIPE,
                 stdout=procutil.stdout,
                 stderr=procutil.stderr,
                 env=procutil.tonativeenv(procutil.shellenviron(env)),
             )
         except OSError as e:
             if e.errno == errno.ENOENT and not shell:
                 self.warn(
                     _(b"missing pager command '%s', skipping pager\n") % command
                 )
                 return False
             raise
 
         # back up original file descriptors
         stdoutfd = os.dup(procutil.stdout.fileno())
         stderrfd = os.dup(procutil.stderr.fileno())
 
         os.dup2(pager.stdin.fileno(), procutil.stdout.fileno())
         if self._isatty(procutil.stderr):
             os.dup2(pager.stdin.fileno(), procutil.stderr.fileno())
 
         @self.atexit
         def killpager():
             if util.safehasattr(signal, b"SIGINT"):
                 signal.signal(signal.SIGINT, signal.SIG_IGN)
             # restore original fds, closing pager.stdin copies in the process
             os.dup2(stdoutfd, procutil.stdout.fileno())
             os.dup2(stderrfd, procutil.stderr.fileno())
             pager.stdin.close()
             pager.wait()
 
         return True
 
     @property
     def _exithandlers(self):
         return _reqexithandlers
 
     def atexit(self, func, *args, **kwargs):
         """register a function to run after dispatching a request
 
         Handlers do not stay registered across request boundaries."""
         self._exithandlers.append((func, args, kwargs))
         return func
 
     def interface(self, feature):
         """what interface to use for interactive console features?
 
         The interface is controlled by the value of `ui.interface` but also by
         the value of feature-specific configuration. For example:
 
         ui.interface.histedit = text
         ui.interface.chunkselector = curses
 
         Here the features are "histedit" and "chunkselector".
 
         The configuration above means that the default interfaces for commands
         is curses, the interface for histedit is text and the interface for
         selecting chunk is crecord (the best curses interface available).
 
         Consider the following example:
         ui.interface = curses
         ui.interface.histedit = text
 
         Then histedit will use the text interface and chunkselector will use
         the default curses interface (crecord at the moment).
         """
         alldefaults = frozenset([b"text", b"curses"])
 
         featureinterfaces = {
             b"chunkselector": [
                 b"text",
                 b"curses",
             ],
             b"histedit": [
                 b"text",
                 b"curses",
             ],
         }
 
         # Feature-specific interface
         if feature not in featureinterfaces.keys():
             # Programming error, not user error
             raise ValueError(b"Unknown feature requested %s" % feature)
 
         availableinterfaces = frozenset(featureinterfaces[feature])
         if alldefaults > availableinterfaces:
             # Programming error, not user error. We need a use case to
             # define the right thing to do here.
             raise ValueError(
                 b"Feature %s does not handle all default interfaces" % feature
             )
 
         if self.plain() or encoding.environ.get(b'TERM') == b'dumb':
             return b"text"
 
         # Default interface for all the features
         defaultinterface = b"text"
         i = self.config(b"ui", b"interface")
         if i in alldefaults:
             defaultinterface = i
 
         choseninterface = defaultinterface
         f = self.config(b"ui", b"interface.%s" % feature)
         if f in availableinterfaces:
             choseninterface = f
 
         if i is not None and defaultinterface != i:
             if f is not None:
                 self.warn(_(b"invalid value for ui.interface: %s\n") % (i,))
             else:
                 self.warn(
                     _(b"invalid value for ui.interface: %s (using %s)\n")
                     % (i, choseninterface)
                 )
         if f is not None and choseninterface != f:
             self.warn(
                 _(b"invalid value for ui.interface.%s: %s (using %s)\n")
                 % (feature, f, choseninterface)
             )
 
         return choseninterface
 
     def interactive(self):
         """is interactive input allowed?
 
         An interactive session is a session where input can be reasonably read
         from `sys.stdin'. If this function returns false, any attempt to read
         from stdin should fail with an error, unless a sensible default has been
         specified.
 
         Interactiveness is triggered by the value of the `ui.interactive'
         configuration variable or - if it is unset - when `sys.stdin' points
         to a terminal device.
 
         This function refers to input only; for output, see `ui.formatted()'.
         """
         i = self.configbool(b"ui", b"interactive")
         if i is None:
             # some environments replace stdin without implementing isatty
             # usually those are non-interactive
             return self._isatty(self._fin)
 
         return i
 
     def termwidth(self):
         """how wide is the terminal in columns?"""
         if b'COLUMNS' in encoding.environ:
             try:
                 return int(encoding.environ[b'COLUMNS'])
             except ValueError:
                 pass
         return scmutil.termsize(self)[0]
 
     def formatted(self):
         """should formatted output be used?
 
         It is often desirable to format the output to suite the output medium.
         Examples of this are truncating long lines or colorizing messages.
         However, this is not often not desirable when piping output into other
         utilities, e.g. `grep'.
 
         Formatted output is triggered by the value of the `ui.formatted'
         configuration variable or - if it is unset - when `sys.stdout' points
         to a terminal device. Please note that `ui.formatted' should be
         considered an implementation detail; it is not intended for use outside
         Mercurial or its extensions.
 
         This function refers to output only; for input, see `ui.interactive()'.
         This function always returns false when in plain mode, see `ui.plain()'.
         """
         if self.plain():
             return False
 
         i = self.configbool(b"ui", b"formatted")
         if i is None:
             # some environments replace stdout without implementing isatty
             # usually those are non-interactive
             return self._isatty(self._fout)
 
         return i
 
     def _readline(self, prompt=b' ', promptopts=None):
         # Replacing stdin/stdout temporarily is a hard problem on Python 3
         # because they have to be text streams with *no buffering*. Instead,
         # we use rawinput() only if call_readline() will be invoked by
         # PyOS_Readline(), so no I/O will be made at Python layer.
         usereadline = (
             self._isatty(self._fin)
             and self._isatty(self._fout)
             and procutil.isstdin(self._fin)
             and procutil.isstdout(self._fout)
         )
         if usereadline:
             try:
                 # magically add command line editing support, where
                 # available
                 import readline
 
                 # force demandimport to really load the module
                 readline.read_history_file
                 # windows sometimes raises something other than ImportError
             except Exception:
                 usereadline = False
 
         if self._colormode == b'win32' or not usereadline:
             if not promptopts:
                 promptopts = {}
             self._writemsgnobuf(
                 self._fmsgout, prompt, type=b'prompt', **promptopts
             )
             self.flush()
             prompt = b' '
         else:
             prompt = self.label(prompt, b'ui.prompt') + b' '
 
         # prompt ' ' must exist; otherwise readline may delete entire line
         # - http://bugs.python.org/issue12833
         with self.timeblockedsection(b'stdio'):
             if usereadline:
                 self.flush()
                 prompt = encoding.strfromlocal(prompt)
                 line = encoding.strtolocal(pycompat.rawinput(prompt))
                 # When stdin is in binary mode on Windows, it can cause
                 # raw_input() to emit an extra trailing carriage return
                 if pycompat.oslinesep == b'\r\n' and line.endswith(b'\r'):
                     line = line[:-1]
             else:
                 self._fout.write(pycompat.bytestr(prompt))
                 self._fout.flush()
                 line = self._fin.readline()
                 if not line:
                     raise EOFError
                 line = line.rstrip(pycompat.oslinesep)
 
         return line
 
     def prompt(self, msg, default=b"y"):
         """Prompt user with msg, read response.
         If ui is not interactive, the default is returned.
         """
         return self._prompt(msg, default=default)
 
     def _prompt(self, msg, **opts):
         default = opts['default']
         if not self.interactive():
             self._writemsg(self._fmsgout, msg, b' ', type=b'prompt', **opts)
             self._writemsg(
                 self._fmsgout, default or b'', b"\n", type=b'promptecho'
             )
             return default
         try:
             r = self._readline(prompt=msg, promptopts=opts)
             if not r:
                 r = default
             if self.configbool(b'ui', b'promptecho'):
                 self._writemsg(
                     self._fmsgout, r or b'', b"\n", type=b'promptecho'
                 )
             return r
         except EOFError:
             raise error.ResponseExpected()
 
     @staticmethod
     def extractchoices(prompt):
         """Extract prompt message and list of choices from specified prompt.
 
         This returns tuple "(message, choices)", and "choices" is the
         list of tuple "(response character, text without &)".
 
         >>> ui.extractchoices(b"awake? $$ &Yes $$ &No")
         ('awake? ', [('y', 'Yes'), ('n', 'No')])
         >>> ui.extractchoices(b"line\\nbreak? $$ &Yes $$ &No")
         ('line\\nbreak? ', [('y', 'Yes'), ('n', 'No')])
         >>> ui.extractchoices(b"want lots of $$money$$?$$Ye&s$$N&o")
         ('want lots of $$money$$?', [('s', 'Yes'), ('o', 'No')])
         """
 
         # Sadly, the prompt string may have been built with a filename
         # containing "$$" so let's try to find the first valid-looking
         # prompt to start parsing. Sadly, we also can't rely on
         # choices containing spaces, ASCII, or basically anything
         # except an ampersand followed by a character.
         m = re.match(br'(?s)(.+?)\$\$([^$]*&[^ $].*)', prompt)
         msg = m.group(1)
         choices = [p.strip(b' ') for p in m.group(2).split(b'$$')]
 
         def choicetuple(s):
             ampidx = s.index(b'&')
             return s[ampidx + 1 : ampidx + 2].lower(), s.replace(b'&', b'', 1)
 
         return (msg, [choicetuple(s) for s in choices])
 
     def promptchoice(self, prompt, default=0):
         """Prompt user with a message, read response, and ensure it matches
         one of the provided choices. The prompt is formatted as follows:
 
            "would you like fries with that (Yn)? $$ &Yes $$ &No"
 
         The index of the choice is returned. Responses are case
         insensitive. If ui is not interactive, the default is
         returned.
         """
 
         msg, choices = self.extractchoices(prompt)
         resps = [r for r, t in choices]
         while True:
             r = self._prompt(msg, default=resps[default], choices=choices)
             if r.lower() in resps:
                 return resps.index(r.lower())
             # TODO: shouldn't it be a warning?
             self._writemsg(self._fmsgout, _(b"unrecognized response\n"))
 
     def getpass(self, prompt=None, default=None):
         if not self.interactive():
             return default
         try:
             self._writemsg(
                 self._fmsgerr,
                 prompt or _(b'password: '),
                 type=b'prompt',
                 password=True,
             )
             # disable getpass() only if explicitly specified. it's still valid
             # to interact with tty even if fin is not a tty.
             with self.timeblockedsection(b'stdio'):
                 if self.configbool(b'ui', b'nontty'):
                     l = self._fin.readline()
                     if not l:
                         raise EOFError
                     return l.rstrip(b'\n')
                 else:
                     return encoding.strtolocal(getpass.getpass(''))
         except EOFError:
             raise error.ResponseExpected()
 
     def status(self, *msg, **opts):
         """write status message to output (if ui.quiet is False)
 
         This adds an output label of "ui.status".
         """
         if not self.quiet:
             self._writemsg(self._fmsgout, type=b'status', *msg, **opts)
 
     def warn(self, *msg, **opts):
         """write warning message to output (stderr)
 
         This adds an output label of "ui.warning".
         """
         self._writemsg(self._fmsgerr, type=b'warning', *msg, **opts)
 
     def error(self, *msg, **opts):
         """write error message to output (stderr)
 
         This adds an output label of "ui.error".
         """
         self._writemsg(self._fmsgerr, type=b'error', *msg, **opts)
 
     def note(self, *msg, **opts):
         """write note to output (if ui.verbose is True)
 
         This adds an output label of "ui.note".
         """
         if self.verbose:
             self._writemsg(self._fmsgout, type=b'note', *msg, **opts)
 
     def debug(self, *msg, **opts):
         """write debug message to output (if ui.debugflag is True)
 
         This adds an output label of "ui.debug".
         """
         if self.debugflag:
             self._writemsg(self._fmsgout, type=b'debug', *msg, **opts)
             self.log(b'debug', b'%s', b''.join(msg))
 
     # Aliases to defeat check-code.
     statusnoi18n = status
     notenoi18n = note
     warnnoi18n = warn
     writenoi18n = write
 
     def edit(
         self,
         text,
         user,
         extra=None,
         editform=None,
         pending=None,
         repopath=None,
         action=None,
     ):
         if action is None:
             self.develwarn(
                 b'action is None but will soon be a required '
                 b'parameter to ui.edit()'
             )
         extra_defaults = {
             b'prefix': b'editor',
             b'suffix': b'.txt',
         }
         if extra is not None:
             if extra.get(b'suffix') is not None:
                 self.develwarn(
                     b'extra.suffix is not None but will soon be '
                     b'ignored by ui.edit()'
                 )
             extra_defaults.update(extra)
         extra = extra_defaults
 
         if action == b'diff':
             suffix = b'.diff'
         elif action:
             suffix = b'.%s.hg.txt' % action
         else:
             suffix = extra[b'suffix']
 
         rdir = None
         if self.configbool(b'experimental', b'editortmpinhg'):
             rdir = repopath
         (fd, name) = pycompat.mkstemp(
             prefix=b'hg-' + extra[b'prefix'] + b'-', suffix=suffix, dir=rdir
         )
         try:
             with os.fdopen(fd, 'wb') as f:
                 f.write(util.tonativeeol(text))
 
             environ = {b'HGUSER': user}
             if b'transplant_source' in extra:
                 environ.update(
                     {b'HGREVISION': hex(extra[b'transplant_source'])}
                 )
             for label in (b'intermediate-source', b'source', b'rebase_source'):
                 if label in extra:
                     environ.update({b'HGREVISION': extra[label]})
                     break
             if editform:
                 environ.update({b'HGEDITFORM': editform})
             if pending:
                 environ.update({b'HG_PENDING': pending})
 
             editor = self.geteditor()
 
             self.system(
                 b"%s \"%s\"" % (editor, name),
                 environ=environ,
                 onerr=error.CanceledError,
                 errprefix=_(b"edit failed"),
                 blockedtag=b'editor',
             )
 
             with open(name, 'rb') as f:
                 t = util.fromnativeeol(f.read())
         finally:
             os.unlink(name)
 
         return t
 
     def system(
         self,
         cmd,
         environ=None,
         cwd=None,
         onerr=None,
         errprefix=None,
         blockedtag=None,
     ):
         """execute shell command with appropriate output stream. command
         output will be redirected if fout is not stdout.
 
         if command fails and onerr is None, return status, else raise onerr
         object as exception.
         """
         if blockedtag is None:
             # Long cmds tend to be because of an absolute path on cmd. Keep
             # the tail end instead
             cmdsuffix = cmd.translate(None, _keepalnum)[-85:]
             blockedtag = b'unknown_system_' + cmdsuffix
         out = self._fout
         if any(s[1] for s in self._bufferstates):
             out = self
         with self.timeblockedsection(blockedtag):
             rc = self._runsystem(cmd, environ=environ, cwd=cwd, out=out)
         if rc and onerr:
             errmsg = b'%s %s' % (
                 procutil.shellsplit(cmd)[0],
                 procutil.explainexit(rc),
             )
             if errprefix:
                 errmsg = b'%s: %s' % (errprefix, errmsg)
             raise onerr(errmsg)
         return rc
 
     def _runsystem(self, cmd, environ, cwd, out):
         """actually execute the given shell command (can be overridden by
         extensions like chg)"""
         return procutil.system(cmd, environ=environ, cwd=cwd, out=out)
 
     def traceback(self, exc=None, force=False):
         """print exception traceback if traceback printing enabled or forced.
         only to call in exception handler. returns true if traceback
         printed."""
         if self.tracebackflag or force:
             if exc is None:
                 exc = sys.exc_info()
             cause = getattr(exc[1], 'cause', None)
 
             if cause is not None:
                 causetb = traceback.format_tb(cause[2])
                 exctb = traceback.format_tb(exc[2])
                 exconly = traceback.format_exception_only(cause[0], cause[1])
 
                 # exclude frame where 'exc' was chained and rethrown from exctb
                 self.write_err(
                     b'Traceback (most recent call last):\n',
                     encoding.strtolocal(''.join(exctb[:-1])),
                     encoding.strtolocal(''.join(causetb)),
                     encoding.strtolocal(''.join(exconly)),
                 )
             else:
                 output = traceback.format_exception(exc[0], exc[1], exc[2])
                 self.write_err(encoding.strtolocal(''.join(output)))
         return self.tracebackflag or force
 
     def geteditor(self):
         '''return editor to use'''
         if pycompat.sysplatform == b'plan9':
             # vi is the MIPS instruction simulator on Plan 9. We
             # instead default to E to plumb commit messages to
             # avoid confusion.
             editor = b'E'
         elif pycompat.isdarwin:
             # vi on darwin is POSIX compatible to a fault, and that includes
             # exiting non-zero if you make any mistake when running an ex
             # command. Proof: `vi -c ':unknown' -c ':qa'; echo $?` produces 1,
             # while s/vi/vim/ doesn't.
             editor = b'vim'
         else:
             editor = b'vi'
         return encoding.environ.get(b"HGEDITOR") or self.config(
             b"ui", b"editor", editor
         )
 
     @util.propertycache
     def _progbar(self):
         """setup the progbar singleton to the ui object"""
         if (
             self.quiet
             or self.debugflag
             or self.configbool(b'progress', b'disable')
             or not progress.shouldprint(self)
         ):
             return None
         return getprogbar(self)
 
     def _progclear(self):
         """clear progress bar output if any. use it before any output"""
         if not haveprogbar():  # nothing loaded yet
             return
         if self._progbar is not None and self._progbar.printed:
             self._progbar.clear()
 
     def makeprogress(self, topic, unit=b"", total=None):
         """Create a progress helper for the specified topic"""
         if getattr(self._fmsgerr, 'structured', False):
             # channel for machine-readable output with metadata, just send
             # raw information
             # TODO: consider porting some useful information (e.g. estimated
             # time) from progbar. we might want to support update delay to
             # reduce the cost of transferring progress messages.
             def updatebar(topic, pos, item, unit, total):
                 self._fmsgerr.write(
                     None,
                     type=b'progress',
                     topic=topic,
                     pos=pos,
                     item=item,
                     unit=unit,
                     total=total,
                 )
 
         elif self._progbar is not None:
             updatebar = self._progbar.progress
         else:
 
             def updatebar(topic, pos, item, unit, total):
                 pass
 
         return scmutil.progress(self, updatebar, topic, unit, total)
 
     def getlogger(self, name):
         """Returns a logger of the given name; or None if not registered"""
         return self._loggers.get(name)
 
     def setlogger(self, name, logger):
         """Install logger which can be identified later by the given name
 
         More than one loggers can be registered. Use extension or module
         name to uniquely identify the logger instance.
         """
         self._loggers[name] = logger
 
     def log(self, event, msgfmt, *msgargs, **opts):
         """hook for logging facility extensions
 
         event should be a readily-identifiable subsystem, which will
         allow filtering.
 
         msgfmt should be a newline-terminated format string to log, and
         *msgargs are %-formatted into it.
 
         **opts currently has no defined meanings.
         """
         if not self._loggers:
             return
         activeloggers = [
             l for l in pycompat.itervalues(self._loggers) if l.tracked(event)
         ]
         if not activeloggers:
             return
         msg = msgfmt % msgargs
         opts = pycompat.byteskwargs(opts)
         # guard against recursion from e.g. ui.debug()
         registeredloggers = self._loggers
         self._loggers = {}
         try:
             for logger in activeloggers:
                 logger.log(self, event, msg, opts)
         finally:
             self._loggers = registeredloggers
 
     def label(self, msg, label):
         """style msg based on supplied label
 
         If some color mode is enabled, this will add the necessary control
         characters to apply such color. In addition, 'debug' color mode adds
         markup showing which label affects a piece of text.
 
         ui.write(s, 'label') is equivalent to
         ui.write(ui.label(s, 'label')).
         """
         if self._colormode is not None:
             return color.colorlabel(self, msg, label)
         return msg
 
     def develwarn(self, msg, stacklevel=1, config=None):
         """issue a developer warning message
 
         Use 'stacklevel' to report the offender some layers further up in the
         stack.
         """
         if not self.configbool(b'devel', b'all-warnings'):
             if config is None or not self.configbool(b'devel', config):
                 return
         msg = b'devel-warn: ' + msg
         stacklevel += 1  # get in develwarn
         if self.tracebackflag:
             util.debugstacktrace(msg, stacklevel, self._ferr, self._fout)
             self.log(
                 b'develwarn',
                 b'%s at:\n%s'
                 % (msg, b''.join(util.getstackframes(stacklevel))),
             )
         else:
             curframe = inspect.currentframe()
             calframe = inspect.getouterframes(curframe, 2)
             fname, lineno, fmsg = calframe[stacklevel][1:4]
             fname, fmsg = pycompat.sysbytes(fname), pycompat.sysbytes(fmsg)
             self.write_err(b'%s at: %s:%d (%s)\n' % (msg, fname, lineno, fmsg))
             self.log(
                 b'develwarn', b'%s at: %s:%d (%s)\n', msg, fname, lineno, fmsg
             )
 
             # avoid cycles
             del curframe
             del calframe
 
     def deprecwarn(self, msg, version, stacklevel=2):
         """issue a deprecation warning
 
         - msg: message explaining what is deprecated and how to upgrade,
         - version: last version where the API will be supported,
         """
         if not (
             self.configbool(b'devel', b'all-warnings')
             or self.configbool(b'devel', b'deprec-warn')
         ):
             return
         msg += (
             b"\n(compatibility will be dropped after Mercurial-%s,"
             b" update your code.)"
         ) % version
         self.develwarn(msg, stacklevel=stacklevel, config=b'deprec-warn')
 
     def exportableenviron(self):
         """The environment variables that are safe to export, e.g. through
         hgweb.
         """
         return self._exportableenviron
 
     @contextlib.contextmanager
     def configoverride(self, overrides, source=b""):
         """Context manager for temporary config overrides
         `overrides` must be a dict of the following structure:
         {(section, name) : value}"""
         backups = {}
         try:
             for (section, name), value in overrides.items():
                 backups[(section, name)] = self.backupconfig(section, name)
                 self.setconfig(section, name, value, source)
             yield
         finally:
             for __, backup in backups.items():
                 self.restoreconfig(backup)
             # just restoring ui.quiet config to the previous value is not enough
             # as it does not update ui.quiet class member
             if (b'ui', b'quiet') in overrides:
                 self.fixconfig(section=b'ui')
 
     def estimatememory(self):
         """Provide an estimate for the available system memory in Bytes.
 
         This can be overriden via ui.available-memory. It returns None, if
         no estimate can be computed.
         """
         value = self.config(b'ui', b'available-memory')
         if value is not None:
             try:
                 return util.sizetoint(value)
             except error.ParseError:
                 raise error.ConfigError(
                     _(b"ui.available-memory value is invalid ('%s')") % value
                 )
         return util._estimatememory()
 
 
 class paths(dict):
     """Represents a collection of paths and their configs.
 
     Data is initially derived from ui instances and the config files they have
     loaded.
     """
 
     def __init__(self, ui):
         dict.__init__(self)
 
         for name, loc in ui.configitems(b'paths', ignoresub=True):
             # No location is the same as not existing.
             if not loc:
                 continue
             loc, sub = ui.configsuboptions(b'paths', name)
             self[name] = path(ui, name, rawloc=loc, suboptions=sub)
 
     def getpath(self, name, default=None):
         """Return a ``path`` from a string, falling back to default.
 
         ``name`` can be a named path or locations. Locations are filesystem
         paths or URIs.
 
         Returns None if ``name`` is not a registered path, a URI, or a local
         path to a repo.
         """
         # Only fall back to default if no path was requested.
         if name is None:
             if not default:
                 default = ()
             elif not isinstance(default, (tuple, list)):
                 default = (default,)
             for k in default:
                 try:
                     return self[k]
                 except KeyError:
                     continue
             return None
 
         # Most likely empty string.
         # This may need to raise in the future.
         if not name:
             return None
 
         try:
             return self[name]
         except KeyError:
             # Try to resolve as a local path or URI.
             try:
                 # We don't pass sub-options in, so no need to pass ui instance.
                 return path(None, None, rawloc=name)
             except ValueError:
                 raise error.RepoError(_(b'repository %s does not exist') % name)
 
 
 _pathsuboptions = {}
 
 
 def pathsuboption(option, attr):
     """Decorator used to declare a path sub-option.
 
     Arguments are the sub-option name and the attribute it should set on
     ``path`` instances.
 
     The decorated function will receive as arguments a ``ui`` instance,
     ``path`` instance, and the string value of this option from the config.
     The function should return the value that will be set on the ``path``
     instance.
 
     This decorator can be used to perform additional verification of
     sub-options and to change the type of sub-options.
     """
 
     def register(func):
         _pathsuboptions[option] = (attr, func)
         return func
 
     return register
 
 
 @pathsuboption(b'pushurl', b'pushloc')
 def pushurlpathoption(ui, path, value):
     u = util.url(value)
     # Actually require a URL.
     if not u.scheme:
         ui.warn(_(b'(paths.%s:pushurl not a URL; ignoring)\n') % path.name)
         return None
 
     # Don't support the #foo syntax in the push URL to declare branch to
     # push.
     if u.fragment:
         ui.warn(
             _(
                 b'("#fragment" in paths.%s:pushurl not supported; '
                 b'ignoring)\n'
             )
             % path.name
         )
         u.fragment = None
 
     return bytes(u)
 
 
 @pathsuboption(b'pushrev', b'pushrev')
 def pushrevpathoption(ui, path, value):
     return value
 
 
 class path(object):
     """Represents an individual path and its configuration."""
 
     def __init__(self, ui, name, rawloc=None, suboptions=None):
         """Construct a path from its config options.
 
         ``ui`` is the ``ui`` instance the path is coming from.
         ``name`` is the symbolic name of the path.
         ``rawloc`` is the raw location, as defined in the config.
         ``pushloc`` is the raw locations pushes should be made to.
 
         If ``name`` is not defined, we require that the location be a) a local
         filesystem path with a .hg directory or b) a URL. If not,
         ``ValueError`` is raised.
         """
         if not rawloc:
             raise ValueError(b'rawloc must be defined')
 
         # Locations may define branches via syntax <base>#<branch>.
         u = util.url(rawloc)
         branch = None
         if u.fragment:
             branch = u.fragment
             u.fragment = None
 
         self.url = u
         self.branch = branch
 
         self.name = name
         self.rawloc = rawloc
         self.loc = b'%s' % u
 
         # When given a raw location but not a symbolic name, validate the
         # location is valid.
         if not name and not u.scheme and not self._isvalidlocalpath(self.loc):
             raise ValueError(
                 b'location is not a URL or path to a local '
                 b'repo: %s' % rawloc
             )
 
         suboptions = suboptions or {}
 
         # Now process the sub-options. If a sub-option is registered, its
         # attribute will always be present. The value will be None if there
         # was no valid sub-option.
         for suboption, (attr, func) in pycompat.iteritems(_pathsuboptions):
             if suboption not in suboptions:
                 setattr(self, attr, None)
                 continue
 
             value = func(ui, self, suboptions[suboption])
             setattr(self, attr, value)
 
     def _isvalidlocalpath(self, path):
         """Returns True if the given path is a potentially valid repository.
         This is its own function so that extensions can change the definition of
         'valid' in this case (like when pulling from a git repo into a hg
         one)."""
         try:
             return os.path.isdir(os.path.join(path, b'.hg'))
         # Python 2 may return TypeError. Python 3, ValueError.
         except (TypeError, ValueError):
             return False
 
     @property
     def suboptions(self):
         """Return sub-options and their values for this path.
 
         This is intended to be used for presentation purposes.
         """
         d = {}
         for subopt, (attr, _func) in pycompat.iteritems(_pathsuboptions):
             value = getattr(self, attr)
             if value is not None:
                 d[subopt] = value
         return d
 
 
 # we instantiate one globally shared progress bar to avoid
 # competing progress bars when multiple UI objects get created
 _progresssingleton = None
 
 
 def getprogbar(ui):
     global _progresssingleton
     if _progresssingleton is None:
         # passing 'ui' object to the singleton is fishy,
         # this is how the extension used to work but feel free to rework it.
         _progresssingleton = progress.progbar(ui)
     return _progresssingleton
 
 
 def haveprogbar():
     return _progresssingleton is not None
 
 
 def _selectmsgdests(ui):
     name = ui.config(b'ui', b'message-output')
     if name == b'channel':
         if ui.fmsg:
             return ui.fmsg, ui.fmsg
         else:
             # fall back to ferr if channel isn't ready so that status/error
             # messages can be printed
             return ui.ferr, ui.ferr
     if name == b'stdio':
         return ui.fout, ui.ferr
     if name == b'stderr':
         return ui.ferr, ui.ferr
     raise error.Abort(b'invalid ui.message-output destination: %s' % name)
 
 
 def _writemsgwith(write, dest, *args, **opts):
     """Write ui message with the given ui._write*() function
 
     The specified message type is translated to 'ui.<type>' label if the dest
     isn't a structured channel, so that the message will be colorized.
     """
     # TODO: maybe change 'type' to a mandatory option
     if 'type' in opts and not getattr(dest, 'structured', False):
         opts['label'] = opts.get('label', b'') + b' ui.%s' % opts.pop('type')
     write(dest, *args, **opts)