diff --git a/rhodecode/lib/oset.py b/rhodecode/lib/oset.py
new file mode 100644
--- /dev/null
+++ b/rhodecode/lib/oset.py
@@ -0,0 +1,64 @@
+KEY, PREV, NEXT = range(3)
+import collections
+
+class OrderedSet(collections.MutableSet):
+
+    def __init__(self, iterable=None):
+        self.end = end = []
+        end += [None, end, end]         # sentinel node for doubly linked list
+        self.map = {}                   # key --> [key, prev, next]
+        if iterable is not None:
+            self |= iterable
+
+    def __len__(self):
+        return len(self.map)
+
+    def __contains__(self, key):
+        return key in self.map
+
+    def add(self, key):
+        if key not in self.map:
+            end = self.end
+            curr = end[PREV]
+            curr[NEXT] = end[PREV] = self.map[key] = [key, curr, end]
+
+    def discard(self, key):
+        if key in self.map:
+            key, prev, next = self.map.pop(key)
+            prev[NEXT] = next
+            next[PREV] = prev
+
+    def __iter__(self):
+        end = self.end
+        curr = end[NEXT]
+        while curr is not end:
+            yield curr[KEY]
+            curr = curr[NEXT]
+
+    def __reversed__(self):
+        end = self.end
+        curr = end[PREV]
+        while curr is not end:
+            yield curr[KEY]
+            curr = curr[PREV]
+
+    def pop(self, last=True):
+        if not self:
+            raise KeyError('set is empty')
+        key = next(reversed(self)) if last else next(iter(self))
+        self.discard(key)
+        return key
+
+    def __repr__(self):
+        if not self:
+            return '%s()' % (self.__class__.__name__,)
+        return '%s(%r)' % (self.__class__.__name__, list(self))
+
+    def __eq__(self, other):
+        if isinstance(other, OrderedSet):
+            return len(self) == len(other) and list(self) == list(other)
+        return set(self) == set(other)
+
+    def __del__(self):
+        self.clear()                    # remove circular references
+