+
+class DiffHandler(BaseHandler):
+    allowed_methods = ('GET',)
+    
+    @hglibrary
+    def read(self, request, source_revision, target_revision, lib):
+        '''Return diff between source_revision and target_revision)'''
+        source_document = lib.document_for_revision(source_revision)
+        target_document = lib.document_for_revision(target_revision)
+        print source_document,
+        print target_document
+        diff = difflib.unified_diff(
+            source_document.data('xml').splitlines(True),
+            target_document.data('xml').splitlines(True),
+            'source',
+            'target')
+        
+        return ''.join(list(diff))
+
+