Handle functions as the value of a hooks.<name> config variable

This should make it easier for extensions to add a hook when
they're loaded.

mercurial/localrepo.py

@@ -142,10 +142,12 b' class localrepository(repo.repository):'
             be run as hooks without wrappers to convert return values.'''
 
             self.ui.note(_("calling hook %s: %s\n") % (hname, funcname))
+            obj = funcname
+            if not callable(obj):
             d = funcname.rfind('.')
             if d == -1:
-                raise util.Abort(_('%s hook is invalid ("%s" not in a module)')
-                                 % (hname, funcname))
+                    raise util.Abort(_('%s hook is invalid ("%s" not in '
+                                       'a module)') % (hname, funcname))
             modname = funcname[:d]
             try:
                 obj = __import__(modname)
@@ -205,7 +207,9 b' class localrepository(repo.repository):'
                  if hname.split(".", 1)[0] == name and cmd]
         hooks.sort()
         for hname, cmd in hooks:
-            if cmd.startswith('python:'):
+            if callable(cmd):
+                r = callhook(hname, cmd) or r
+            elif cmd.startswith('python:'):
                 r = callhook(hname, cmd[7:].strip()) or r
             else:
                 r = runhook(hname, cmd) or r

tests/test-hook

@@ -183,4 +183,24 b" echo 'commit.abort = python:hooktests.ab"
 echo a >> a
 hg --traceback commit -A -m a 2>&1 | grep '^Traceback'
 
+cd ..
+hg init c
+cd c
+
+cat > hookext.py <<EOF
+def autohook(**args):
+    print "Automatically installed hook"
+
+def reposetup(ui, repo):
+    repo.ui.setconfig("hooks", "commit.auto", autohook)
+EOF
+echo '[extensions]' >> .hg/hgrc
+echo 'hookext = hookext.py' >> .hg/hgrc
+
+touch foo
+hg add foo
+hg ci -m 'add foo'
+echo >> foo
+hg ci --debug -m 'change foo' | sed -e 's/ at .*>/>/'
+
 exit 0

tests/test-hook.out

@@ -138,3 +138,7 b' added 1 changesets with 1 changes to 1 f'
 (run 'hg update' to get a working copy)
 # make sure --traceback works
 Traceback (most recent call last):
+Automatically installed hook
+foo
+calling hook commit.auto: <function autohook>
+Automatically installed hook