new file mode 100644
--- /dev/null
+++ b/mercurial/extensions.py
@@ -0,0 +1,69 @@
+# extensions.py - extension handling for mercurial
+#
+# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
+#
+# This software may be used and distributed according to the terms
+# of the GNU General Public License, incorporated herein by reference.
+
+import imp, commands, hg, util
+from i18n import _
+
+_extensions = {}
+
+def find(name):
+    '''return module with given extension name'''
+    try:
+        return _extensions[name]
+    except KeyError:
+        for k, v in _extensions.iteritems():
+            if k.endswith('.' + name) or k.endswith('/' + name) or v == name:
+                return sys.modules[v]
+        raise KeyError(name)
+
+def load(ui, name, path):
+    if name in _extensions:
+        return
+    if path:
+        # the module will be loaded in sys.modules
+        # choose an unique name so that it doesn't
+        # conflicts with other modules
+        module_name = "hgext_%s" % name.replace('.', '_')
+        mod = imp.load_source(module_name, path)
+    else:
+        def importh(name):
+            mod = __import__(name)
+            components = name.split('.')
+            for comp in components[1:]:
+                mod = getattr(mod, comp)
+            return mod
+        try:
+            mod = importh("hgext.%s" % name)
+        except ImportError:
+            mod = importh(name)
+    _extensions[name] = mod
+
+    uisetup = getattr(mod, 'uisetup', None)
+    if uisetup:
+        uisetup(ui)
+    reposetup = getattr(mod, 'reposetup', None)
+    if reposetup:
+        hg.repo_setup_hooks.append(reposetup)
+    cmdtable = getattr(mod, 'cmdtable', {})
+    overrides = [cmd for cmd in cmdtable if cmd in commands.table]
+    if overrides:
+        ui.warn(_("extension '%s' overrides commands: %s\n")
+                % (name, " ".join(overrides)))
+    commands.table.update(cmdtable)
+
+def loadall(ui):
+    for name, path in ui.extensions():
+        try:
+            load(ui, name, path)
+        except (util.SignalInterrupt, KeyboardInterrupt):
+            raise
+        except Exception, inst:
+            ui.warn(_("*** failed to import extension %s: %s\n") %
+                    (name, inst))
+            if ui.print_exc():
+                return 1
+