diff --git a/mercurial/formatter.py b/mercurial/formatter.py
new file mode 100644
--- /dev/null
+++ b/mercurial/formatter.py
@@ -0,0 +1,71 @@
+# formatter.py - generic output formatting for mercurial
+#
+# Copyright 2012 Matt Mackall <mpm@selenic.com>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+class baseformatter(object):
+    def __init__(self, ui, topic, opts):
+        self._ui = ui
+        self._topic = topic
+        self._style = opts.get("style")
+        self._template = opts.get("template")
+        self._item = None
+    def __bool__(self):
+        '''return False if we're not doing real templating so we can
+        skip extra work'''
+        return True
+    def _showitem(self):
+        '''show a formatted item once all data is collected'''
+        pass
+    def startitem(self):
+        '''begin an item in the format list'''
+        if self._item is not None:
+            self._showitem()
+        self._item = {}
+    def data(self, **data):
+        '''insert data into item that's not shown in default output'''
+    def write(self, fields, deftext, *fielddata, **opts):
+        '''do default text output while assigning data to item'''
+        for k, v in zip(fields.split(), fielddata):
+            self._item[k] = v
+    def plain(self, text, **opts):
+        '''show raw text for non-templated mode'''
+        pass
+    def end(self):
+        '''end output for the formatter'''
+        if self._item is not None:
+            self._showitem()
+
+class plainformatter(baseformatter):
+    '''the default text output scheme'''
+    def __init__(self, ui, topic, opts):
+        baseformatter.__init__(self, ui, topic, opts)
+    def __bool__(self):
+        return False
+    def startitem(self):
+        pass
+    def data(self, **data):
+        pass
+    def write(self, fields, deftext, *fielddata, **opts):
+        self._ui.write(deftext % fielddata, **opts)
+    def plain(self, text, **opts):
+        self._ui.write(text, **opts)
+    def end(self):
+        pass
+
+class debugformatter(baseformatter):
+    def __init__(self, ui, topic, opts):
+        baseformatter.__init__(self, ui, topic, opts)
+        self._ui.write("%s = {\n" % self._topic)
+    def _showitem(self):
+        self._ui.write("    " + repr(self._item) + ",\n")
+    def end(self):
+        baseformatter.end(self)
+        self._ui.write("}\n")
+
+def formatter(ui, topic, opts):
+    if ui.configbool('ui', 'formatdebug'):
+        return debugformatter(ui, topic, opts)
+    return plainformatter(ui, topic, opts)