diff --git a/mercurial/extensions.py b/mercurial/extensions.py
--- a/mercurial/extensions.py
+++ b/mercurial/extensions.py
@@ -349,12 +349,13 @@ def disabledcmd(ui, cmd, strict=False):
 
     raise error.UnknownCommand(cmd)
 
-def enabled():
+def enabled(shortname=True):
     '''return a dict of {name: desc} of extensions'''
     exts = {}
     for ename, ext in extensions():
         doc = (gettext(ext.__doc__) or _('(no help text available)'))
-        ename = ename.split('.')[-1]
+        if shortname:
+            ename = ename.split('.')[-1]
         exts[ename] = doc.splitlines()[0].strip()
 
     return exts
diff --git a/mercurial/help.py b/mercurial/help.py
--- a/mercurial/help.py
+++ b/mercurial/help.py
@@ -103,10 +103,11 @@ def topicmatch(kw):
             cmdname = cmd.split('|')[0].lstrip('^')
             results['commands'].append((cmdname, summary))
     for name, docs in itertools.chain(
-        extensions.enabled().iteritems(),
+        extensions.enabled(False).iteritems(),
         extensions.disabled().iteritems()):
         # extensions.load ignores the UI argument
         mod = extensions.load(None, name, '')
+        name = name.split('.')[-1]
         if lowercontains(name) or lowercontains(docs):
             # extension docs are already translated
             results['extensions'].append((name, docs.splitlines()[0]))
diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -200,7 +200,7 @@ class revlog(object):
         self.datafile = indexfile[:-2] + ".d"
         self.opener = opener
         self._cache = None
-        self._basecache = (0, 0)
+        self._basecache = None
         self._chunkcache = (0, '')
         self.index = []
         self._pcache = {}
@@ -1131,6 +1131,8 @@ class revlog(object):
         offset = self.end(prev)
         flags = 0
         d = None
+        if self._basecache is None:
+            self._basecache = (prev, self.chainbase(prev))
         basecache = self._basecache
         p1r, p2r = self.rev(p1), self.rev(p2)
 
diff --git a/tests/test-generaldelta.t b/tests/test-generaldelta.t
new file mode 100755
--- /dev/null
+++ b/tests/test-generaldelta.t
@@ -0,0 +1,23 @@
+Check whether size of generaldelta revlog is not bigger than its
+regular equivalent. Test would fail if generaldelta was naive
+implementation of parentdelta: third manifest revision would be fully
+inserted due to big distance from its paren revision (zero).
+
+  $ hg init repo
+  $ cd repo
+  $ echo foo > foo
+  $ echo bar > bar
+  $ hg commit -q -Am boo
+  $ hg clone --pull . ../gdrepo -q --config format.generaldelta=yes
+  $ for r in 1 2 3; do
+  >   echo $r > foo
+  >   hg commit -q -m $r
+  >   hg up -q -r 0
+  >   hg pull . -q -r $r -R ../gdrepo
+  > done
+  $ cd ..
+  $ regsize=`du -s -b repo/.hg/store/00manifest.i | cut -f 1`
+  $ gdsize=`du -s -b gdrepo/.hg/store/00manifest.i | cut -f 1`
+  $ if ((regsize < gdsize)); then
+  >   echo 'generaldelta increased size of a revlog!'
+  > fi
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -773,6 +773,12 @@ Test help hooks
 
 Test keyword search help
 
+  $ cat > prefixedname.py <<EOF
+  > '''matched against word "clone"
+  > '''
+  > EOF
+  $ echo '[extensions]' >> $HGRCPATH
+  $ echo "dot.dot.prefixedname = `pwd`/prefixedname.py" >> $HGRCPATH
   $ hg help -k clone
   Topics:
   
@@ -792,7 +798,8 @@ Test keyword search help
   
   Extensions:
   
-   relink recreates hardlinks between repository clones
+   prefixedname matched against word "clone"
+   relink       recreates hardlinks between repository clones
   
   Extension Commands: