mercurial/help.py

rust: switch hg-core and hg-cpython to rust 2018 edition

Many interesting changes have happened in Rust since the Oxidation Plan was
introduced, like the 2018 edition and procedural macros:

    - Opting in to the 2018 edition is a clear benefit in terms of future
      proofing, new (nice to have) syntactical sugar notwithstanding. It
      also has a new non-lexical, non-AST based borrow checker that has
      fewer bugs(!) and allows us to write correct code that in some cases
      would have been rejected by the old one.
    - Procedural macros allow us to use the PyO3 crate which maintainers have
      expressed the clear goal of compiling on stable, which would help in
      code maintainability compared to rust-cpython.

In this patch are the following changes:
    - Removing most `extern crate` uses
    - Updating `use` clauses (`crate` keyword, nested `use`)
    - Removing `mod.rs` in favor of an aptly named module file

Like discussed in the mailing list (
https://www.mercurial-scm.org/pipermail/mercurial-devel/2019-July/132316.html
), until Rust integration in Mercurial is considered to be out of the
experimental phase, the maximum version of Rust allowed is whatever the latest
version Debian packages.

Differential Revision: https://phab.mercurial-scm.org/D6597

# help.py - help data for mercurial
#
# Copyright 2006 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 itertools
import os
import re
import textwrap

from .i18n import (
    _,
    gettext,
)
from . import (
    cmdutil,
    encoding,
    error,
    extensions,
    fancyopts,
    filemerge,
    fileset,
    minirst,
    pycompat,
    registrar,
    revset,
    templatefilters,
    templatefuncs,
    templatekw,
    ui as uimod,
    util,
)
from .hgweb import (
    webcommands,
)
from .utils import (
    compression,
)

_exclkeywords = {
    "(ADVANCED)",
    "(DEPRECATED)",
    "(EXPERIMENTAL)",
    # i18n: "(ADVANCED)" is a keyword, must be translated consistently
    _("(ADVANCED)"),
    # i18n: "(DEPRECATED)" is a keyword, must be translated consistently
    _("(DEPRECATED)"),
    # i18n: "(EXPERIMENTAL)" is a keyword, must be translated consistently
    _("(EXPERIMENTAL)"),
}

# The order in which command categories will be displayed.
# Extensions with custom categories should insert them into this list
# after/before the appropriate item, rather than replacing the list or
# assuming absolute positions.
CATEGORY_ORDER = [
    registrar.command.CATEGORY_REPO_CREATION,
    registrar.command.CATEGORY_REMOTE_REPO_MANAGEMENT,
    registrar.command.CATEGORY_COMMITTING,
    registrar.command.CATEGORY_CHANGE_MANAGEMENT,
    registrar.command.CATEGORY_CHANGE_ORGANIZATION,
    registrar.command.CATEGORY_FILE_CONTENTS,
    registrar.command.CATEGORY_CHANGE_NAVIGATION ,
    registrar.command.CATEGORY_WORKING_DIRECTORY,
    registrar.command.CATEGORY_IMPORT_EXPORT,
    registrar.command.CATEGORY_MAINTENANCE,
    registrar.command.CATEGORY_HELP,
    registrar.command.CATEGORY_MISC,
    registrar.command.CATEGORY_NONE,
]

# Human-readable category names. These are translated.
# Extensions with custom categories should add their names here.
CATEGORY_NAMES = {
    registrar.command.CATEGORY_REPO_CREATION: 'Repository creation',
    registrar.command.CATEGORY_REMOTE_REPO_MANAGEMENT:
        'Remote repository management',
    registrar.command.CATEGORY_COMMITTING: 'Change creation',
    registrar.command.CATEGORY_CHANGE_NAVIGATION: 'Change navigation',
    registrar.command.CATEGORY_CHANGE_MANAGEMENT: 'Change manipulation',
    registrar.command.CATEGORY_CHANGE_ORGANIZATION: 'Change organization',
    registrar.command.CATEGORY_WORKING_DIRECTORY:
        'Working directory management',
    registrar.command.CATEGORY_FILE_CONTENTS: 'File content management',
    registrar.command.CATEGORY_IMPORT_EXPORT: 'Change import/export',
    registrar.command.CATEGORY_MAINTENANCE: 'Repository maintenance',
    registrar.command.CATEGORY_HELP: 'Help',
    registrar.command.CATEGORY_MISC: 'Miscellaneous commands',
    registrar.command.CATEGORY_NONE: 'Uncategorized commands',
}

# Topic categories.
TOPIC_CATEGORY_IDS = 'ids'
TOPIC_CATEGORY_OUTPUT = 'output'
TOPIC_CATEGORY_CONFIG = 'config'
TOPIC_CATEGORY_CONCEPTS = 'concepts'
TOPIC_CATEGORY_MISC = 'misc'
TOPIC_CATEGORY_NONE = 'none'

# The order in which topic categories will be displayed.
# Extensions with custom categories should insert them into this list
# after/before the appropriate item, rather than replacing the list or
# assuming absolute positions.
TOPIC_CATEGORY_ORDER = [
    TOPIC_CATEGORY_IDS,
    TOPIC_CATEGORY_OUTPUT,
    TOPIC_CATEGORY_CONFIG,
    TOPIC_CATEGORY_CONCEPTS,
    TOPIC_CATEGORY_MISC,
    TOPIC_CATEGORY_NONE,
]

# Human-readable topic category names. These are translated.
TOPIC_CATEGORY_NAMES = {
    TOPIC_CATEGORY_IDS: 'Mercurial identifiers',
    TOPIC_CATEGORY_OUTPUT: 'Mercurial output',
    TOPIC_CATEGORY_CONFIG: 'Mercurial configuration',
    TOPIC_CATEGORY_CONCEPTS: 'Concepts',
    TOPIC_CATEGORY_MISC: 'Miscellaneous',
    TOPIC_CATEGORY_NONE: 'Uncategorized topics',
}

def listexts(header, exts, indent=1, showdeprecated=False):
    '''return a text listing of the given extensions'''
    rst = []
    if exts:
        for name, desc in sorted(exts.iteritems()):
            if not showdeprecated and any(w in desc for w in _exclkeywords):
                continue
            rst.append('%s:%s: %s\n' % (' ' * indent, name, desc))
    if rst:
        rst.insert(0, '\n%s\n\n' % header)
    return rst

def extshelp(ui):
    rst = loaddoc('extensions')(ui).splitlines(True)
    rst.extend(listexts(
        _('enabled extensions:'), extensions.enabled(), showdeprecated=True))
    rst.extend(listexts(_('disabled extensions:'), extensions.disabled(),
                        showdeprecated=ui.verbose))
    doc = ''.join(rst)
    return doc

def optrst(header, options, verbose):
    data = []
    multioccur = False
    for option in options:
        if len(option) == 5:
            shortopt, longopt, default, desc, optlabel = option
        else:
            shortopt, longopt, default, desc = option
            optlabel = _("VALUE") # default label

        if not verbose and any(w in desc for w in _exclkeywords):
            continue

        so = ''
        if shortopt:
            so = '-' + shortopt
        lo = '--' + longopt
        if default is True:
            lo = '--[no-]' + longopt

        if isinstance(default, fancyopts.customopt):
            default = default.getdefaultvalue()
        if default and not callable(default):
            # default is of unknown type, and in Python 2 we abused
            # the %s-shows-repr property to handle integers etc. To
            # match that behavior on Python 3, we do str(default) and
            # then convert it to bytes.
            defaultstr = pycompat.bytestr(default)
            if default is True:
                defaultstr = _("on")
            desc += _(" (default: %s)") % defaultstr

        if isinstance(default, list):
            lo += " %s [+]" % optlabel
            multioccur = True
        elif (default is not None) and not isinstance(default, bool):
            lo += " %s" % optlabel

        data.append((so, lo, desc))

    if multioccur:
        header += (_(" ([+] can be repeated)"))

    rst = ['\n%s:\n\n' % header]
    rst.extend(minirst.maketable(data, 1))

    return ''.join(rst)

def indicateomitted(rst, omitted, notomitted=None):
    rst.append('\n\n.. container:: omitted\n\n    %s\n\n' % omitted)
    if notomitted:
        rst.append('\n\n.. container:: notomitted\n\n    %s\n\n' % notomitted)

def filtercmd(ui, cmd, func, kw, doc):
    if not ui.debugflag and cmd.startswith("debug") and kw != "debug":
        # Debug command, and user is not looking for those.
        return True
    if not ui.verbose:
        if not kw and not doc:
            # Command had no documentation, no point in showing it by default.
            return True
        if getattr(func, 'alias', False) and not getattr(func, 'owndoc', False):
            # Alias didn't have its own documentation.
            return True
        if doc and any(w in doc for w in _exclkeywords):
            # Documentation has excluded keywords.
            return True
    if kw == "shortlist" and not getattr(func, 'helpbasic', False):
        # We're presenting the short list but the command is not basic.
        return True
    if ui.configbool('help', 'hidden-command.%s' % cmd):
        # Configuration explicitly hides the command.
        return True
    return False

def filtertopic(ui, topic):
    return ui.configbool('help', 'hidden-topic.%s' % topic, False)

def topicmatch(ui, commands, kw):
    """Return help topics matching kw.

    Returns {'section': [(name, summary), ...], ...} where section is
    one of topics, commands, extensions, or extensioncommands.
    """
    kw = encoding.lower(kw)
    def lowercontains(container):
        return kw in encoding.lower(container)  # translated in helptable
    results = {'topics': [],
               'commands': [],
               'extensions': [],
               'extensioncommands': [],
               }
    for topic in helptable:
        names, header, doc = topic[0:3]
        # Old extensions may use a str as doc.
        if (sum(map(lowercontains, names))
            or lowercontains(header)
            or (callable(doc) and lowercontains(doc(ui)))):
            name = names[0]
            if not filtertopic(ui, name):
                results['topics'].append((names[0], header))
    for cmd, entry in commands.table.iteritems():
        if len(entry) == 3:
            summary = entry[2]
        else:
            summary = ''
        # translate docs *before* searching there
        func = entry[0]
        docs = _(pycompat.getdoc(func)) or ''
        if kw in cmd or lowercontains(summary) or lowercontains(docs):
            doclines = docs.splitlines()
            if doclines:
                summary = doclines[0]
            cmdname = cmdutil.parsealiases(cmd)[0]
            if filtercmd(ui, cmdname, func, kw, docs):
                continue
            results['commands'].append((cmdname, summary))
    for name, docs in itertools.chain(
        extensions.enabled(False).iteritems(),
        extensions.disabled().iteritems()):
        if not docs:
            continue
        name = name.rpartition('.')[-1]
        if lowercontains(name) or lowercontains(docs):
            # extension docs are already translated
            results['extensions'].append((name, docs.splitlines()[0]))
        try:
            mod = extensions.load(ui, name, '')
        except ImportError:
            # debug message would be printed in extensions.load()
            continue
        for cmd, entry in getattr(mod, 'cmdtable', {}).iteritems():
            if kw in cmd or (len(entry) > 2 and lowercontains(entry[2])):
                cmdname = cmdutil.parsealiases(cmd)[0]
                func = entry[0]
                cmddoc = pycompat.getdoc(func)
                if cmddoc:
                    cmddoc = gettext(cmddoc).splitlines()[0]
                else:
                    cmddoc = _('(no help text available)')
                if filtercmd(ui, cmdname, func, kw, cmddoc):
                    continue
                results['extensioncommands'].append((cmdname, cmddoc))
    return results

def loaddoc(topic, subdir=None):
    """Return a delayed loader for help/topic.txt."""

    def loader(ui):
        docdir = os.path.join(util.datapath, 'help')
        if subdir:
            docdir = os.path.join(docdir, subdir)
        path = os.path.join(docdir, topic + ".txt")
        doc = gettext(util.readfile(path))
        for rewriter in helphooks.get(topic, []):
            doc = rewriter(ui, topic, doc)
        return doc

    return loader

internalstable = sorted([
    (['bundle2'], _('Bundle2'),
     loaddoc('bundle2', subdir='internals')),
    (['bundles'], _('Bundles'),
     loaddoc('bundles', subdir='internals')),
    (['cbor'], _('CBOR'),
     loaddoc('cbor', subdir='internals')),
    (['censor'], _('Censor'),
     loaddoc('censor', subdir='internals')),
    (['changegroups'], _('Changegroups'),
     loaddoc('changegroups', subdir='internals')),
    (['config'], _('Config Registrar'),
     loaddoc('config', subdir='internals')),
    (['extensions', 'extension'], _('Extension API'),
     loaddoc('extensions', subdir='internals')),
    (['mergestate'], _('Mergestate'),
     loaddoc('mergestate', subdir='internals')),
    (['requirements'], _('Repository Requirements'),
     loaddoc('requirements', subdir='internals')),
    (['revlogs'], _('Revision Logs'),
     loaddoc('revlogs', subdir='internals')),
    (['wireprotocol'], _('Wire Protocol'),
     loaddoc('wireprotocol', subdir='internals')),
    (['wireprotocolrpc'], _('Wire Protocol RPC'),
     loaddoc('wireprotocolrpc', subdir='internals')),
    (['wireprotocolv2'], _('Wire Protocol Version 2'),
     loaddoc('wireprotocolv2', subdir='internals')),
])

def internalshelp(ui):
    """Generate the index for the "internals" topic."""
    lines = ['To access a subtopic, use "hg help internals.{subtopic-name}"\n',
             '\n']
    for names, header, doc in internalstable:
        lines.append(' :%s: %s\n' % (names[0], header))

    return ''.join(lines)

helptable = sorted([
    (['bundlespec'], _("Bundle File Formats"), loaddoc('bundlespec'),
     TOPIC_CATEGORY_CONCEPTS),
    (['color'], _("Colorizing Outputs"), loaddoc('color'),
     TOPIC_CATEGORY_OUTPUT),
    (["config", "hgrc"], _("Configuration Files"), loaddoc('config'),
     TOPIC_CATEGORY_CONFIG),
    (['deprecated'], _("Deprecated Features"), loaddoc('deprecated'),
     TOPIC_CATEGORY_MISC),
    (["dates"], _("Date Formats"), loaddoc('dates'), TOPIC_CATEGORY_OUTPUT),
    (["flags"], _("Command-line flags"), loaddoc('flags'),
     TOPIC_CATEGORY_CONFIG),
    (["patterns"], _("File Name Patterns"), loaddoc('patterns'),
     TOPIC_CATEGORY_IDS),
    (['environment', 'env'], _('Environment Variables'),
     loaddoc('environment'), TOPIC_CATEGORY_CONFIG),
    (['revisions', 'revs', 'revsets', 'revset', 'multirevs', 'mrevs'],
      _('Specifying Revisions'), loaddoc('revisions'), TOPIC_CATEGORY_IDS),
    (['filesets', 'fileset'], _("Specifying File Sets"), loaddoc('filesets'),
     TOPIC_CATEGORY_IDS),
    (['diffs'], _('Diff Formats'), loaddoc('diffs'), TOPIC_CATEGORY_OUTPUT),
    (['merge-tools', 'mergetools', 'mergetool'], _('Merge Tools'),
     loaddoc('merge-tools'), TOPIC_CATEGORY_CONFIG),
    (['templating', 'templates', 'template', 'style'], _('Template Usage'),
     loaddoc('templates'), TOPIC_CATEGORY_OUTPUT),
    (['urls'], _('URL Paths'), loaddoc('urls'), TOPIC_CATEGORY_IDS),
    (["extensions"], _("Using Additional Features"), extshelp,
     TOPIC_CATEGORY_CONFIG),
    (["subrepos", "subrepo"], _("Subrepositories"), loaddoc('subrepos'),
     TOPIC_CATEGORY_CONCEPTS),
    (["hgweb"], _("Configuring hgweb"), loaddoc('hgweb'),
     TOPIC_CATEGORY_CONFIG),
    (["glossary"], _("Glossary"), loaddoc('glossary'), TOPIC_CATEGORY_CONCEPTS),
    (["hgignore", "ignore"], _("Syntax for Mercurial Ignore Files"),
     loaddoc('hgignore'), TOPIC_CATEGORY_IDS),
    (["phases"], _("Working with Phases"), loaddoc('phases'),
     TOPIC_CATEGORY_CONCEPTS),
    (['scripting'], _('Using Mercurial from scripts and automation'),
     loaddoc('scripting'), TOPIC_CATEGORY_MISC),
    (['internals'], _("Technical implementation topics"), internalshelp,
     TOPIC_CATEGORY_MISC),
    (['pager'], _("Pager Support"), loaddoc('pager'), TOPIC_CATEGORY_CONFIG),
])

# Maps topics with sub-topics to a list of their sub-topics.
subtopics = {
    'internals': internalstable,
}

# Map topics to lists of callable taking the current topic help and
# returning the updated version
helphooks = {}

def addtopichook(topic, rewriter):
    helphooks.setdefault(topic, []).append(rewriter)

def makeitemsdoc(ui, topic, doc, marker, items, dedent=False):
    """Extract docstring from the items key to function mapping, build a
    single documentation block and use it to overwrite the marker in doc.
    """
    entries = []
    for name in sorted(items):
        text = (pycompat.getdoc(items[name]) or '').rstrip()
        if (not text
            or not ui.verbose and any(w in text for w in _exclkeywords)):
            continue
        text = gettext(text)
        if dedent:
            # Abuse latin1 to use textwrap.dedent() on bytes.
            text = textwrap.dedent(text.decode('latin1')).encode('latin1')
        lines = text.splitlines()
        doclines = [(lines[0])]
        for l in lines[1:]:
            # Stop once we find some Python doctest
            if l.strip().startswith('>>>'):
                break
            if dedent:
                doclines.append(l.rstrip())
            else:
                doclines.append('  ' + l.strip())
        entries.append('\n'.join(doclines))
    entries = '\n\n'.join(entries)
    return doc.replace(marker, entries)

def addtopicsymbols(topic, marker, symbols, dedent=False):
    def add(ui, topic, doc):
        return makeitemsdoc(ui, topic, doc, marker, symbols, dedent=dedent)
    addtopichook(topic, add)

addtopicsymbols('bundlespec', '.. bundlecompressionmarker',
                compression.bundlecompressiontopics())
addtopicsymbols('filesets', '.. predicatesmarker', fileset.symbols)
addtopicsymbols('merge-tools', '.. internaltoolsmarker',
                filemerge.internalsdoc)
addtopicsymbols('revisions', '.. predicatesmarker', revset.symbols)
addtopicsymbols('templates', '.. keywordsmarker', templatekw.keywords)
addtopicsymbols('templates', '.. filtersmarker', templatefilters.filters)
addtopicsymbols('templates', '.. functionsmarker', templatefuncs.funcs)
addtopicsymbols('hgweb', '.. webcommandsmarker', webcommands.commands,
                dedent=True)

def inserttweakrc(ui, topic, doc):
    marker = '.. tweakdefaultsmarker'
    repl = uimod.tweakrc
    def sub(m):
        lines = [m.group(1) + s for s in repl.splitlines()]
        return '\n'.join(lines)
    return re.sub(br'( *)%s' % re.escape(marker), sub, doc)

addtopichook('config', inserttweakrc)

def help_(ui, commands, name, unknowncmd=False, full=True, subtopic=None,
          fullname=None, **opts):
    '''
    Generate the help for 'name' as unformatted restructured text. If
    'name' is None, describe the commands available.
    '''

    opts = pycompat.byteskwargs(opts)

    def helpcmd(name, subtopic=None):
        try:
            aliases, entry = cmdutil.findcmd(name, commands.table,
                                             strict=unknowncmd)
        except error.AmbiguousCommand as inst:
            # py3 fix: except vars can't be used outside the scope of the
            # except block, nor can be used inside a lambda. python issue4617
            prefix = inst.args[0]
            select = lambda c: cmdutil.parsealiases(c)[0].startswith(prefix)
            rst = helplist(select)
            return rst

        rst = []

        # check if it's an invalid alias and display its error if it is
        if getattr(entry[0], 'badalias', None):
            rst.append(entry[0].badalias + '\n')
            if entry[0].unknowncmd:
                try:
                    rst.extend(helpextcmd(entry[0].cmdname))
                except error.UnknownCommand:
                    pass
            return rst

        # synopsis
        if len(entry) > 2:
            if entry[2].startswith('hg'):
                rst.append("%s\n" % entry[2])
            else:
                rst.append('hg %s %s\n' % (aliases[0], entry[2]))
        else:
            rst.append('hg %s\n' % aliases[0])
        # aliases
        if full and not ui.quiet and len(aliases) > 1:
            rst.append(_("\naliases: %s\n") % ', '.join(aliases[1:]))
        rst.append('\n')

        # description
        doc = gettext(pycompat.getdoc(entry[0]))
        if not doc:
            doc = _("(no help text available)")
        if util.safehasattr(entry[0], 'definition'):  # aliased command
            source = entry[0].source
            if entry[0].definition.startswith('!'):  # shell alias
                doc = (_('shell alias for: %s\n\n%s\n\ndefined by: %s\n') %
                       (entry[0].definition[1:], doc, source))
            else:
                doc = (_('alias for: hg %s\n\n%s\n\ndefined by: %s\n') %
                       (entry[0].definition, doc, source))
        doc = doc.splitlines(True)
        if ui.quiet or not full:
            rst.append(doc[0])
        else:
            rst.extend(doc)
        rst.append('\n')

        # check if this command shadows a non-trivial (multi-line)
        # extension help text
        try:
            mod = extensions.find(name)
            doc = gettext(pycompat.getdoc(mod)) or ''
            if '\n' in doc.strip():
                msg = _("(use 'hg help -e %s' to show help for "
                        "the %s extension)") % (name, name)
                rst.append('\n%s\n' % msg)
        except KeyError:
            pass

        # options
        if not ui.quiet and entry[1]:
            rst.append(optrst(_("options"), entry[1], ui.verbose))

        if ui.verbose:
            rst.append(optrst(_("global options"),
                              commands.globalopts, ui.verbose))

        if not ui.verbose:
            if not full:
                rst.append(_("\n(use 'hg %s -h' to show more help)\n")
                           % name)
            elif not ui.quiet:
                rst.append(_('\n(some details hidden, use --verbose '
                               'to show complete help)'))

        return rst

    def helplist(select=None, **opts):
        # Category -> list of commands
        cats = {}
        # Command -> short description
        h = {}
        # Command -> string showing synonyms
        syns = {}
        for c, e in commands.table.iteritems():
            fs = cmdutil.parsealiases(c)
            f = fs[0]
            syns[f] = ', '.join(fs)
            func = e[0]
            if select and not select(f):
                continue
            doc = pycompat.getdoc(func)
            if filtercmd(ui, f, func, name, doc):
                continue
            doc = gettext(doc)
            if not doc:
                doc = _("(no help text available)")
            h[f] = doc.splitlines()[0].rstrip()

            cat = getattr(func, 'helpcategory', None) or (
                registrar.command.CATEGORY_NONE)
            cats.setdefault(cat, []).append(f)

        rst = []
        if not h:
            if not ui.quiet:
                rst.append(_('no commands defined\n'))
            return rst

        # Output top header.
        if not ui.quiet:
            if name == "shortlist":
                rst.append(_('basic commands:\n\n'))
            elif name == "debug":
                rst.append(_('debug commands (internal and unsupported):\n\n'))
            else:
                rst.append(_('list of commands:\n'))

        def appendcmds(cmds):
            cmds = sorted(cmds)
            for c in cmds:
                if ui.verbose:
                    rst.append(" :%s: %s\n" % (syns[c], h[c]))
                else:
                    rst.append(' :%s: %s\n' % (c, h[c]))

        if name in ('shortlist', 'debug'):
            # List without categories.
            appendcmds(h)
        else:
            # Check that all categories have an order.
            missing_order = set(cats.keys()) - set(CATEGORY_ORDER)
            if missing_order:
                ui.develwarn('help categories missing from CATEGORY_ORDER: %s' %
                             missing_order)

            # List per category.
            for cat in CATEGORY_ORDER:
                catfns = cats.get(cat, [])
                if catfns:
                    if len(cats) > 1:
                        catname = gettext(CATEGORY_NAMES[cat])
                        rst.append("\n%s:\n" % catname)
                    rst.append("\n")
                    appendcmds(catfns)

        ex = opts.get
        anyopts = (ex(r'keyword') or not (ex(r'command') or ex(r'extension')))
        if not name and anyopts:
            exts = listexts(_('enabled extensions:'), extensions.enabled(),
                            showdeprecated=ui.verbose)
            if exts:
                rst.append('\n')
                rst.extend(exts)

            rst.append(_("\nadditional help topics:\n"))
            # Group commands by category.
            topiccats = {}
            for topic in helptable:
                names, header, doc = topic[0:3]
                if len(topic) > 3 and topic[3]:
                    category = topic[3]
                else:
                    category = TOPIC_CATEGORY_NONE

                topicname = names[0]
                if not filtertopic(ui, topicname):
                    topiccats.setdefault(category, []).append(
                        (topicname, header))

            # Check that all categories have an order.
            missing_order = set(topiccats.keys()) - set(TOPIC_CATEGORY_ORDER)
            if missing_order:
                ui.develwarn(
                    'help categories missing from TOPIC_CATEGORY_ORDER: %s' %
                    missing_order)

            # Output topics per category.
            for cat in TOPIC_CATEGORY_ORDER:
                topics = topiccats.get(cat, [])
                if topics:
                    if len(topiccats) > 1:
                        catname = gettext(TOPIC_CATEGORY_NAMES[cat])
                        rst.append("\n%s:\n" % catname)
                    rst.append("\n")
                    for t, desc in topics:
                        rst.append(" :%s: %s\n" % (t, desc))

        if ui.quiet:
            pass
        elif ui.verbose:
            rst.append('\n%s\n' % optrst(_("global options"),
                                         commands.globalopts, ui.verbose))
            if name == 'shortlist':
                rst.append(_("\n(use 'hg help' for the full list "
                             "of commands)\n"))
        else:
            if name == 'shortlist':
                rst.append(_("\n(use 'hg help' for the full list of commands "
                             "or 'hg -v' for details)\n"))
            elif name and not full:
                rst.append(_("\n(use 'hg help %s' to show the full help "
                             "text)\n") % name)
            elif name and syns and name in syns.keys():
                rst.append(_("\n(use 'hg help -v -e %s' to show built-in "
                             "aliases and global options)\n") % name)
            else:
                rst.append(_("\n(use 'hg help -v%s' to show built-in aliases "
                             "and global options)\n")
                           % (name and " " + name or ""))
        return rst

    def helptopic(name, subtopic=None):
        # Look for sub-topic entry first.
        header, doc = None, None
        if subtopic and name in subtopics:
            for names, header, doc in subtopics[name]:
                if subtopic in names:
                    break
            if not any(subtopic in s[0] for s in subtopics[name]):
                raise error.UnknownCommand(name)

        if not header:
            for topic in helptable:
                names, header, doc = topic[0:3]
                if name in names:
                    break
            else:
                raise error.UnknownCommand(name)

        rst = [minirst.section(header)]

        # description
        if not doc:
            rst.append("    %s\n" % _("(no help text available)"))
        if callable(doc):
            rst += ["    %s\n" % l for l in doc(ui).splitlines()]

        if not ui.verbose:
            omitted = _('(some details hidden, use --verbose'
                         ' to show complete help)')
            indicateomitted(rst, omitted)

        try:
            cmdutil.findcmd(name, commands.table)
            rst.append(_("\nuse 'hg help -c %s' to see help for "
                       "the %s command\n") % (name, name))
        except error.UnknownCommand:
            pass
        return rst

    def helpext(name, subtopic=None):
        try:
            mod = extensions.find(name)
            doc = gettext(pycompat.getdoc(mod)) or _('no help text available')
        except KeyError:
            mod = None
            doc = extensions.disabledext(name)
            if not doc:
                raise error.UnknownCommand(name)

        if '\n' not in doc:
            head, tail = doc, ""
        else:
            head, tail = doc.split('\n', 1)
        rst = [_('%s extension - %s\n\n') % (name.rpartition('.')[-1], head)]
        if tail:
            rst.extend(tail.splitlines(True))
            rst.append('\n')

        if not ui.verbose:
            omitted = _('(some details hidden, use --verbose'
                         ' to show complete help)')
            indicateomitted(rst, omitted)

        if mod:
            try:
                ct = mod.cmdtable
            except AttributeError:
                ct = {}
            modcmds = {c.partition('|')[0] for c in ct}
            rst.extend(helplist(modcmds.__contains__))
        else:
            rst.append(_("(use 'hg help extensions' for information on enabling"
                       " extensions)\n"))
        return rst

    def helpextcmd(name, subtopic=None):
        cmd, ext, doc = extensions.disabledcmd(ui, name,
                                               ui.configbool('ui', 'strict'))
        doc = doc.splitlines()[0]

        rst = listexts(_("'%s' is provided by the following "
                              "extension:") % cmd, {ext: doc}, indent=4,
                       showdeprecated=True)
        rst.append('\n')
        rst.append(_("(use 'hg help extensions' for information on enabling "
                   "extensions)\n"))
        return rst


    rst = []
    kw = opts.get('keyword')
    if kw or name is None and any(opts[o] for o in opts):
        matches = topicmatch(ui, commands, name or '')
        helpareas = []
        if opts.get('extension'):
            helpareas += [('extensions', _('Extensions'))]
        if opts.get('command'):
            helpareas += [('commands', _('Commands'))]
        if not helpareas:
            helpareas = [('topics', _('Topics')),
                         ('commands', _('Commands')),
                         ('extensions', _('Extensions')),
                         ('extensioncommands', _('Extension Commands'))]
        for t, title in helpareas:
            if matches[t]:
                rst.append('%s:\n\n' % title)
                rst.extend(minirst.maketable(sorted(matches[t]), 1))
                rst.append('\n')
        if not rst:
            msg = _('no matches')
            hint = _("try 'hg help' for a list of topics")
            raise error.Abort(msg, hint=hint)
    elif name and name != 'shortlist':
        queries = []
        if unknowncmd:
            queries += [helpextcmd]
        if opts.get('extension'):
            queries += [helpext]
        if opts.get('command'):
            queries += [helpcmd]
        if not queries:
            queries = (helptopic, helpcmd, helpext, helpextcmd)
        for f in queries:
            try:
                rst = f(name, subtopic)
                break
            except error.UnknownCommand:
                pass
        else:
            if unknowncmd:
                raise error.UnknownCommand(name)
            else:
                if fullname:
                    formatname = fullname
                else:
                    formatname = name
                if subtopic:
                    hintname = subtopic
                else:
                    hintname = name
                msg = _('no such help topic: %s') % formatname
                hint = _("try 'hg help --keyword %s'") % hintname
                raise error.Abort(msg, hint=hint)
    else:
        # program name
        if not ui.quiet:
            rst = [_("Mercurial Distributed SCM\n"), '\n']
        rst.extend(helplist(None, **pycompat.strkwargs(opts)))

    return ''.join(rst)

def formattedhelp(ui, commands, fullname, keep=None, unknowncmd=False,
                  full=True, **opts):
    """get help for a given topic (as a dotted name) as rendered rst

    Either returns the rendered help text or raises an exception.
    """
    if keep is None:
        keep = []
    else:
        keep = list(keep) # make a copy so we can mutate this later

    # <fullname> := <name>[.<subtopic][.<section>]
    name = subtopic = section = None
    if fullname is not None:
        nameparts = fullname.split('.')
        name = nameparts.pop(0)
        if nameparts and name in subtopics:
            subtopic = nameparts.pop(0)
        if nameparts:
            section = encoding.lower('.'.join(nameparts))

    textwidth = ui.configint('ui', 'textwidth')
    termwidth = ui.termwidth() - 2
    if textwidth <= 0 or termwidth < textwidth:
        textwidth = termwidth
    text = help_(ui, commands, name, fullname=fullname,
                 subtopic=subtopic, unknowncmd=unknowncmd, full=full, **opts)

    blocks, pruned = minirst.parse(text, keep=keep)
    if 'verbose' in pruned:
        keep.append('omitted')
    else:
        keep.append('notomitted')
    blocks, pruned = minirst.parse(text, keep=keep)
    if section:
        blocks = minirst.filtersections(blocks, section)

    # We could have been given a weird ".foo" section without a name
    # to look for, or we could have simply failed to found "foo.bar"
    # because bar isn't a section of foo
    if section and not (blocks and name):
        raise error.Abort(_("help section not found: %s") % fullname)

    return minirst.formatplain(blocks, textwidth)