hgweb: replace some str.split() calls by str.partition() or str.rpartition()

Since Python 2.5 str has new methods: partition and rpartition. They are more
specialized than the usual split and rsplit, and they sometimes convey the
intent of code better and also are a bit faster (faster than split/rsplit with
maxsplit specified). Let's use them in appropriate places for a small speedup.

Example performance (partition):

$ python -m timeit 'assert "apple|orange|banana".split("|")[0] == "apple"'
1000000 loops, best of 3: 0.376 usec per loop

$ python -m timeit 'assert "apple|orange|banana".split("|", 1)[0] == "apple"'
1000000 loops, best of 3: 0.327 usec per loop

$ python -m timeit 'assert "apple|orange|banana".partition("|")[0] == "apple"'
1000000 loops, best of 3: 0.214 usec per loop

Example performance (rpartition):

$ python -m timeit 'assert "apple|orange|banana".rsplit("|")[-1] == "banana"'
1000000 loops, best of 3: 0.372 usec per loop

$ python -m timeit 'assert "apple|orange|banana".rsplit("|", 1)[-1] == "banana"'
1000000 loops, best of 3: 0.332 usec per loop

$ python -m timeit 'assert "apple|orange|banana".rpartition("|")[-1] == "banana"'
1000000 loops, best of 3: 0.219 usec per loop

mercurial/hgweb/hgweb_mod.py

@@ -304,8 +304,8 b' class hgweb(object):'
                 parts = parts[len(repo_parts):]
             query = '/'.join(parts)
         else:
-            query = req.env['QUERY_STRING'].split('&', 1)[0]
-            query = query.split(';', 1)[0]
+            query = req.env['QUERY_STRING'].partition('&')[0]
+            query = query.partition(';')[0]
 
         # process this if it's a protocol request
         # protocol bits don't need to create any URLs

mercurial/hgweb/request.py

@@ -80,7 +80,7 b' class wsgirequest(object):'
         if self._start_response is not None:
             self.headers.append(('Content-Type', type))
             if filename:
-                filename = (filename.split('/')[-1]
+                filename = (filename.rpartition('/')[-1]
                             .replace('\\', '\\\\').replace('"', '\\"'))
                 self.headers.append(('Content-Disposition',
                                      'inline; filename="%s"' % filename))

mercurial/hgweb/webcommands.py

@@ -1248,7 +1248,7 b' def graph(web, req, tmpl):'
 def _getdoc(e):
     doc = e[0].__doc__
     if doc:
-        doc = _(doc).split('\n')[0]
+        doc = _(doc).partition('\n')[0]
     else:
         doc = _('(no help text available)')
     return doc
@@ -1278,7 +1278,7 b' def help(web, req, tmpl):'
                 yield {'topic': entries[0], 'summary': summary}
 
         early, other = [], []
-        primary = lambda s: s.split('|')[0]
+        primary = lambda s: s.partition('|')[0]
         for c, e in commands.table.iteritems():
             doc = _getdoc(e)
             if 'DEPRECATED' in doc or c.startswith('debug'):