doc: use an absolute path in sys.path to work around a python DLL loading bug

This bug[1] was causing the zstd entry under "Available Compression Engines" to
be omitted from the documentation for some versions of python3.  I could
upgrade, but past upgrades have broken venvs and clobbered installed packages.
It's a trivial workaround, so there's no sense in leaving this subtle issue.  It
was flushed out by changing the module policy here from 'allow' to 'c', and
seeing this error:

    ImportError: DLL load failed while importing parsers: The parameter is incorrect.

[1] https://github.com/python/cpython/issues/87271

Differential Revision: https://phab.mercurial-scm.org/D12599

doc/gendoc.py

@@ -1,346 +1,346 b''
 #!/usr/bin/env python3
 """usage: %s DOC ...
 
 where DOC is the name of a document
 """
 
 from __future__ import absolute_import
 
 import os
 import sys
 import textwrap
 
 try:
     import msvcrt
 
     msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
     msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY)
 except ImportError:
     pass
 
 # This script is executed during installs and may not have C extensions
 # available. Relax C module requirements.
 os.environ['HGMODULEPOLICY'] = 'allow'
 # import from the live mercurial repo
-sys.path.insert(0, "..")
+sys.path.insert(0, os.path.abspath(".."))
 from mercurial import demandimport
 
 demandimport.enable()
 
 from mercurial import (
     commands,
     encoding,
     extensions,
     fancyopts,
     help,
     minirst,
     pycompat,
     ui as uimod,
 )
 from mercurial.i18n import (
     gettext,
     _,
 )
 from mercurial.utils import stringutil
 
 table = commands.table
 globalopts = commands.globalopts
 helptable = help.helptable
 loaddoc = help.loaddoc
 
 
 def get_desc(docstr):
     if not docstr:
         return b"", b""
     # sanitize
     docstr = docstr.strip(b"\n")
     docstr = docstr.rstrip()
     shortdesc = docstr.splitlines()[0].strip()
 
     i = docstr.find(b"\n")
     if i != -1:
         desc = docstr[i + 2 :]
     else:
         desc = shortdesc
 
     desc = textwrap.dedent(desc.decode('latin1')).encode('latin1')
 
     return (shortdesc, desc)
 
 
 def get_opts(opts):
     for opt in opts:
         if len(opt) == 5:
             shortopt, longopt, default, desc, optlabel = opt
         else:
             shortopt, longopt, default, desc = opt
             optlabel = _(b"VALUE")
         allopts = []
         if shortopt:
             allopts.append(b"-%s" % shortopt)
         if longopt:
             allopts.append(b"--%s" % longopt)
         if isinstance(default, list):
             allopts[-1] += b" <%s[+]>" % optlabel
         elif (default is not None) and not isinstance(default, bool):
             allopts[-1] += b" <%s>" % optlabel
         if b'\n' in desc:
             # only remove line breaks and indentation
             desc = b' '.join(l.lstrip() for l in desc.split(b'\n'))
         if isinstance(default, fancyopts.customopt):
             default = default.getdefaultvalue()
         if default:
             default = stringutil.forcebytestr(default)
             desc += _(b" (default: %s)") % default
         yield (b", ".join(allopts), desc)
 
 
 def get_cmd(cmd, cmdtable):
     d = {}
     attr = cmdtable[cmd]
     cmds = cmd.lstrip(b"^").split(b"|")
 
     d[b'cmd'] = cmds[0]
     d[b'aliases'] = cmd.split(b"|")[1:]
     d[b'desc'] = get_desc(gettext(pycompat.getdoc(attr[0])))
     d[b'opts'] = list(get_opts(attr[1]))
 
     s = b'hg ' + cmds[0]
     if len(attr) > 2:
         if not attr[2].startswith(b'hg'):
             s += b' ' + attr[2]
         else:
             s = attr[2]
     d[b'synopsis'] = s.strip()
 
     return d
 
 
 def showdoc(ui):
     # print options
     ui.write(minirst.section(_(b"Options")))
     multioccur = False
     for optstr, desc in get_opts(globalopts):
         ui.write(b"%s\n    %s\n\n" % (optstr, desc))
         if optstr.endswith(b"[+]>"):
             multioccur = True
     if multioccur:
         ui.write(_(b"\n[+] marked option can be specified multiple times\n"))
         ui.write(b"\n")
 
     # print cmds
     ui.write(minirst.section(_(b"Commands")))
     commandprinter(ui, table, minirst.subsection, minirst.subsubsection)
 
     # print help topics
     # The config help topic is included in the hgrc.5 man page.
     helpprinter(ui, helptable, minirst.section, exclude=[b'config'])
 
     ui.write(minirst.section(_(b"Extensions")))
     ui.write(
         _(
             b"This section contains help for extensions that are "
             b"distributed together with Mercurial. Help for other "
             b"extensions is available in the help system."
         )
     )
     ui.write(
         (
             b"\n\n"
             b".. contents::\n"
             b"   :class: htmlonly\n"
             b"   :local:\n"
             b"   :depth: 1\n\n"
         )
     )
 
     for extensionname in sorted(allextensionnames()):
         mod = extensions.load(ui, extensionname, None)
         ui.write(minirst.subsection(extensionname))
         ui.write(b"%s\n\n" % gettext(pycompat.getdoc(mod)))
         cmdtable = getattr(mod, 'cmdtable', None)
         if cmdtable:
             ui.write(minirst.subsubsection(_(b'Commands')))
             commandprinter(
                 ui,
                 cmdtable,
                 minirst.subsubsubsection,
                 minirst.subsubsubsubsection,
             )
 
 
 def showtopic(ui, topic):
     extrahelptable = [
         ([b"common"], b'', loaddoc(b'common'), help.TOPIC_CATEGORY_MISC),
         ([b"hg.1"], b'', loaddoc(b'hg.1'), help.TOPIC_CATEGORY_CONFIG),
         ([b"hg-ssh.8"], b'', loaddoc(b'hg-ssh.8'), help.TOPIC_CATEGORY_CONFIG),
         (
             [b"hgignore.5"],
             b'',
             loaddoc(b'hgignore.5'),
             help.TOPIC_CATEGORY_CONFIG,
         ),
         ([b"hgrc.5"], b'', loaddoc(b'hgrc.5'), help.TOPIC_CATEGORY_CONFIG),
         (
             [b"hgignore.5.gendoc"],
             b'',
             loaddoc(b'hgignore'),
             help.TOPIC_CATEGORY_CONFIG,
         ),
         (
             [b"hgrc.5.gendoc"],
             b'',
             loaddoc(b'config'),
             help.TOPIC_CATEGORY_CONFIG,
         ),
     ]
     helpprinter(ui, helptable + extrahelptable, None, include=[topic])
 
 
 def helpprinter(ui, helptable, sectionfunc, include=[], exclude=[]):
     for h in helptable:
         names, sec, doc = h[0:3]
         if exclude and names[0] in exclude:
             continue
         if include and names[0] not in include:
             continue
         for name in names:
             ui.write(b".. _%s:\n" % name)
         ui.write(b"\n")
         if sectionfunc:
             ui.write(sectionfunc(sec))
         if callable(doc):
             doc = doc(ui)
         ui.write(doc)
         ui.write(b"\n")
 
 
 def commandprinter(ui, cmdtable, sectionfunc, subsectionfunc):
     """Render restructuredtext describing a list of commands and their
     documentations, grouped by command category.
 
     Args:
       ui: UI object to write the output to
       cmdtable: a dict that maps a string of the command name plus its aliases
         (separated with pipes) to a 3-tuple of (the command's function, a list
         of its option descriptions, and a string summarizing available
         options). Example, with aliases added for demonstration purposes:
 
           'phase|alias1|alias2': (
              <function phase at 0x7f0816b05e60>,
              [ ('p', 'public', False, 'set changeset phase to public'),
                ...,
                ('r', 'rev', [], 'target revision', 'REV')],
              '[-p|-d|-s] [-f] [-r] [REV...]'
           )
       sectionfunc: minirst function to format command category headers
       subsectionfunc: minirst function to format command headers
     """
     h = {}
     for c, attr in cmdtable.items():
         f = c.split(b"|")[0]
         f = f.lstrip(b"^")
         h[f] = c
     cmds = h.keys()
 
     def helpcategory(cmd):
         """Given a canonical command name from `cmds` (above), retrieve its
         help category. If helpcategory is None, default to CATEGORY_NONE.
         """
         fullname = h[cmd]
         details = cmdtable[fullname]
         helpcategory = details[0].helpcategory
         return helpcategory or help.registrar.command.CATEGORY_NONE
 
     cmdsbycategory = {category: [] for category in help.CATEGORY_ORDER}
     for cmd in cmds:
         # If a command category wasn't registered, the command won't get
         # rendered below, so we raise an AssertionError.
         if helpcategory(cmd) not in cmdsbycategory:
             raise AssertionError(
                 "The following command did not register its (category) in "
                 "help.CATEGORY_ORDER: %s (%s)" % (cmd, helpcategory(cmd))
             )
         cmdsbycategory[helpcategory(cmd)].append(cmd)
 
     # Print the help for each command. We present the commands grouped by
     # category, and we use help.CATEGORY_ORDER as a guide for a helpful order
     # in which to present the categories.
     for category in help.CATEGORY_ORDER:
         categorycmds = cmdsbycategory[category]
         if not categorycmds:
             # Skip empty categories
             continue
         # Print a section header for the category.
         # For now, the category header is at the same level as the headers for
         # the commands in the category; this is fixed in the next commit.
         ui.write(sectionfunc(help.CATEGORY_NAMES[category]))
         # Print each command in the category
         for f in sorted(categorycmds):
             if f.startswith(b"debug"):
                 continue
             d = get_cmd(h[f], cmdtable)
             ui.write(subsectionfunc(d[b'cmd']))
             # short description
             ui.write(d[b'desc'][0])
             # synopsis
             ui.write(b"::\n\n")
             synopsislines = d[b'synopsis'].splitlines()
             for line in synopsislines:
                 # some commands (such as rebase) have a multi-line
                 # synopsis
                 ui.write(b"   %s\n" % line)
             ui.write(b'\n')
             # description
             ui.write(b"%s\n\n" % d[b'desc'][1])
             # options
             opt_output = list(d[b'opts'])
             if opt_output:
                 opts_len = max([len(line[0]) for line in opt_output])
                 ui.write(_(b"Options:\n\n"))
                 multioccur = False
                 for optstr, desc in opt_output:
                     if desc:
                         s = b"%-*s  %s" % (opts_len, optstr, desc)
                     else:
                         s = optstr
                     ui.write(b"%s\n" % s)
                     if optstr.endswith(b"[+]>"):
                         multioccur = True
                 if multioccur:
                     ui.write(
                         _(
                             b"\n[+] marked option can be specified"
                             b" multiple times\n"
                         )
                     )
                 ui.write(b"\n")
             # aliases
             if d[b'aliases']:
                 # Note the empty comment, this is required to separate this
                 # (which should be a blockquote) from any preceding things (such
                 # as a definition list).
                 ui.write(
                     _(b"..\n\n    aliases: %s\n\n") % b" ".join(d[b'aliases'])
                 )
 
 
 def allextensionnames():
     return set(extensions.enabled().keys()) | set(extensions.disabled().keys())
 
 
 if __name__ == "__main__":
     doc = b'hg.1.gendoc'
     if len(sys.argv) > 1:
         doc = encoding.strtolocal(sys.argv[1])
 
     ui = uimod.ui.load()
     # Trigger extensions to load. This is disabled by default because it uses
     # the current user's configuration, which is often not what is wanted.
     if encoding.environ.get(b'GENDOC_LOAD_CONFIGURED_EXTENSIONS', b'0') != b'0':
         extensions.loadall(ui)
 
     if doc == b'hg.1.gendoc':
         showdoc(ui)
     else:
         showtopic(ui, encoding.strtolocal(sys.argv[1]))