--- a/mercurial/archival.py
+++ b/mercurial/archival.py
@@ -200,8 +200,9 @@ def archive(repo, dest, node, kind, deco
 
     prefix is name of path to put before every archive member.'''
 
-    def write(name, mode, islink, data):
+    def write(name, mode, islink, getdata):
         if matchfn and not matchfn(name): return
+        data = getdata()
         if decode:
             data = repo.wwritedata(name, data)
         archiver.addfile(name, mode, islink, data)
@@ -212,8 +213,8 @@ def archive(repo, dest, node, kind, deco
     items = m.items()
     items.sort()
     write('.hg_archival.txt', 0644, False,
-          'repo: %s\nnode: %s\n' % (hex(repo.changelog.node(0)), hex(node)))
+          lambda: 'repo: %s\nnode: %s\n' % (hex(repo.changelog.node(0)), hex(node)))
     for filename, filenode in items:
         write(filename, m.execf(filename) and 0755 or 0644, m.linkf(filename),
-              repo.file(filename).read(filenode))
+              lambda: repo.file(filename).read(filenode))
     archiver.done()

--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -1355,7 +1355,7 @@ def help_(ui, name=None, with_version=Fa
 
             addglobalopts(False)
 
-    def helplist(select=None):
+    def helplist(header, select=None):
         h = {}
         cmds = {}
         for c, e in table.items():
@@ -1373,6 +1373,11 @@ def help_(ui, name=None, with_version=Fa
             h[f] = doc.splitlines(0)[0].rstrip()
             cmds[f] = c.lstrip("^")
 
+        if not h:
+            ui.status(_('no commands defined\n'))
+            return
+
+        ui.status(header)
         fns = h.keys()
         fns.sort()
         m = max(map(len, fns))
@@ -1422,14 +1427,10 @@ def help_(ui, name=None, with_version=Fa
         try:
             ct = mod.cmdtable
         except AttributeError:
-            ct = None
-        if not ct:
-            ui.status(_('no commands defined\n'))
-            return
-
-        ui.status(_('list of commands:\n\n'))
+            ct = {}
+
         modcmds = dict.fromkeys([c.split('|', 1)[0] for c in ct])
-        helplist(modcmds.has_key)
+        helplist(_('list of commands:\n\n'), modcmds.has_key)
 
     if name and name != 'shortlist':
         i = None
@@ -1453,11 +1454,11 @@ def help_(ui, name=None, with_version=Fa
 
         # list of commands
         if name == "shortlist":
-            ui.status(_('basic commands:\n\n'))
+            header = _('basic commands:\n\n')
         else:
-            ui.status(_('list of commands:\n\n'))
-
-        helplist()
+            header = _('list of commands:\n\n')
+
+        helplist(header)
 
     # list all option lists
     opt_output = []

--- a/mercurial/dirstate.py
+++ b/mercurial/dirstate.py
@@ -21,6 +21,7 @@ class dirstate(object):
         self._opener = opener
         self._root = root
         self._dirty = 0
+        self._dirtypl = 0
         self._ui = ui
 
     def __getattr__(self, name):
@@ -114,6 +115,7 @@ class dirstate(object):
 
     def setparents(self, p1, p2=nullid):
         self.markdirty()
+        self._dirtypl = 1
         self._pl = p1, p2
 
     def setbranch(self, branch):
@@ -126,7 +128,8 @@ class dirstate(object):
     def _read(self):
         self._map = {}
         self._copymap = {}
-        self._pl = [nullid, nullid]
+        if not self._dirtypl:
+            self._pl = [nullid, nullid]
         try:
             st = self._opener("dirstate").read()
         except IOError, err:
@@ -135,7 +138,8 @@ class dirstate(object):
         if not st:
             return
 
-        self._pl = [st[:20], st[20: 40]]
+        if not self._dirtypl:
+            self._pl = [st[:20], st[20: 40]]
 
         # deref fields so they will be local in loop
         dmap = self._map
@@ -160,8 +164,8 @@ class dirstate(object):
 
     def invalidate(self):
         for a in "_map _copymap _branch _pl _dirs _ignore".split():
-            if hasattr(self, a):
-                self.__delattr__(a)
+            if a in self.__dict__:
+                delattr(self, a)
         self._dirty = 0
 
     def copy(self, source, dest):
@@ -262,6 +266,7 @@ class dirstate(object):
         st.write(cs.getvalue())
         st.rename()
         self._dirty = 0
+        self._dirtypl = 0
 
     def filterfiles(self, files):
         ret = {}

--- a/tests/test-extension
+++ b/tests/test-extension
@@ -64,3 +64,18 @@ emptypath=`pwd`/empty.py
 echo '[extensions]' > $HGRCPATH
 echo "empty = $emptypath" >> $HGRCPATH
 hg help empty
+
+cat > debugextension.py <<EOF
+'''only debugcommands
+'''
+def debugfoobar(ui, repo, *args, **opts):
+    "yet another debug command"
+    pass
+
+cmdtable = {"debugfoobar": (debugfoobar, (), "hg debugfoobar")}
+EOF
+debugpath=`pwd`/debugextension.py
+echo '[extensions]' > $HGRCPATH
+echo "debugextension = $debugpath" >> $HGRCPATH
+hg help debugextension
+hg --debug help debugextension

--- a/tests/test-extension.out
+++ b/tests/test-extension.out
@@ -22,3 +22,30 @@ Foo
 empty extension - empty cmdtable
 
 no commands defined
+debugextension extension - only debugcommands
+
+no commands defined
+debugextension extension - only debugcommands
+
+list of commands:
+
+ debugfoobar:
+      yet another debug command
+
+global options:
+ -R --repository      repository root directory or symbolic path name
+    --cwd             change working directory
+ -y --noninteractive  do not prompt, assume 'yes' for any required answers
+ -q --quiet           suppress output
+ -v --verbose         enable additional output
+    --config          set/override config option
+    --debug           enable debugging output
+    --debugger        start debugger
+    --encoding        set the charset encoding (default: ascii)
+    --encodingmode    set the charset encoding mode (default: strict)
+    --lsprof          print improved command execution profile
+    --traceback       print traceback on exception
+    --time            time how long the command takes
+    --profile         print command execution profile
+    --version         output version information and exit
+ -h --help            display help and exit