interhg: upgrade comments to online help and improve them

Some inspiration taken from the wiki page of the extension.

hgext/interhg.py

@@ -1,82 +1,84 b''
 # interhg.py - interhg
 #
 # Copyright 2007 OHASHI Hideya <[e-mail]>
 #
 # Contributor(s):
 #   Edward Lee <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2, incorporated herein by reference.
-#
-# The `interhg' Mercurial extension allows you to change changelog and
-# summary text just like InterWiki way.
-#
-# To enable this extension:
-#
-#   [extensions]
-#   interhg =
-#
-# These are some example patterns (link to bug tracking, etc.)
-#
-#   [interhg]
-#   issues = s!issue(\d+)!<a href="http://bts/issue\1">issue\1<\/a>!
-#   bugzilla = s!((?:bug|b=|(?=#?\d{4,}))(?:\s*#?)(\d+))!<a..=\2">\1</a>!i
-#   boldify = s/(^|\s)#(\d+)\b/ <b>#\2<\/b>/
-#
-# Add any number of names and patterns to match
+
+'''expand expressions into changelog and summaries
+
+This extension allows the use of a special syntax in summaries,
+which will be automatically expanded into links or any other
+arbitrary expression, much like InterWiki does.
+
+To enable this extension, add the following lines to your hgrc:
+
+  [extensions]
+  interhg =
+
+A few example patterns (link to bug tracking, etc.):
+
+  [interhg]
+  issues = s!issue(\d+)!<a href="http://bts/issue\1">issue\1<\/a>!
+  bugzilla = s!((?:bug|b=|(?=#?\d{4,}))(?:\s*#?)(\d+))!<a..=\2">\1</a>!i
+  boldify = s/(^|\s)#(\d+)\b/ <b>#\2<\/b>/
+'''
 
 import re
 from mercurial.hgweb import hgweb_mod
 from mercurial import templatefilters, extensions
 from mercurial.i18n import _
 
 orig_escape = templatefilters.filters["escape"]
 
 interhg_table = []
 
 def interhg_escape(x):
     escstr = orig_escape(x)
     for regexp, format in interhg_table:
         escstr = regexp.sub(format, escstr)
     return escstr
 
 templatefilters.filters["escape"] = interhg_escape
 
 def interhg_refresh(orig, self):
     interhg_table[:] = []
     for key, pattern in self.repo.ui.configitems('interhg'):
         # grab the delimiter from the character after the "s"
         unesc = pattern[1]
         delim = re.escape(unesc)
 
         # identify portions of the pattern, taking care to avoid escaped
         # delimiters. the replace format and flags are optional, but delimiters
         # are required.
         match = re.match(r'^s%s(.+)(?:(?<=\\\\)|(?<!\\))%s(.*)%s([ilmsux])*$'
                          % (delim, delim, delim), pattern)
         if not match:
             self.repo.ui.warn(_("interhg: invalid pattern for %s: %s\n")
                               % (key, pattern))
             continue
 
         # we need to unescape the delimiter for regexp and format
         delim_re = re.compile(r'(?<!\\)\\%s' % delim)
         regexp = delim_re.sub(unesc, match.group(1))
         format = delim_re.sub(unesc, match.group(2))
 
         # the pattern allows for 6 regexp flags, so set them if necessary
         flagin = match.group(3)
         flags = 0
         if flagin:
             for flag in flagin.upper():
                 flags |= re.__dict__[flag]
 
         try:
             regexp = re.compile(regexp, flags)
             interhg_table.append((regexp, format))
         except re.error:
             self.repo.ui.warn(_("interhg: invalid regexp for %s: %s\n")
                               % (key, regexp))
     return orig(self)
 
 extensions.wrapfunction(hgweb_mod.hgweb, 'refresh', interhg_refresh)