diff --git a/hgext/parentrevspec.py b/hgext/parentrevspec.py
new file mode 100644
--- /dev/null
+++ b/hgext/parentrevspec.py
@@ -0,0 +1,96 @@
+# Mercurial extension to make it easy to refer to the parent of a revision
+#
+# Copyright (C) 2007 Alexis S. L. Carvalho <alexis@cecm.usp.br>
+#
+# This software may be used and distributed according to the terms
+# of the GNU General Public License, incorporated herein by reference.
+'''\
+use suffixes to refer to ancestor revisions
+
+This extension allows you to use git-style suffixes to refer to
+the ancestors of a specific revision.
+
+For example, if you can refer to a revision as "foo", then:
+
+- foo^N = Nth parent of foo:
+  foo^0 = foo
+  foo^1 = first parent of foo
+  foo^2 = second parent of foo
+  foo^  = foo^1
+
+- foo~N = Nth first grandparent of foo
+  foo~0 = foo
+  foo~1 = foo^1 = foo^ = first parent of foo
+  foo~2 = foo^1^1 = foo^^ = first parent of first parent of foo
+'''
+import mercurial.repo
+
+def reposetup(ui, repo):
+    if not repo.local():
+        return
+
+    class parentrevspecrepo(repo.__class__):
+        def lookup(self, key):
+            try:
+                _super = super(parentrevspecrepo, self)
+                return _super.lookup(key)
+            except mercurial.repo.RepoError:
+                pass
+
+            circ = key.find('^')
+            tilde = key.find('~')
+            if circ < 0 and tilde < 0:
+                raise
+            elif circ >= 0 and tilde >= 0:
+                end = min(circ, tilde)
+            else:
+                end = max(circ, tilde)
+
+            cl = self.changelog
+            base = key[:end]
+            try:
+                node = _super.lookup(base)
+            except mercurial.repo.RepoError:
+                # eek - reraise the first error
+                return _super.lookup(key)
+
+            rev = cl.rev(node)
+            suffix = key[end:]
+            i = 0
+            while i < len(suffix):
+                # foo^N => Nth parent of foo
+                # foo^0 == foo
+                # foo^1 == foo^ == 1st parent of foo
+                # foo^2 == 2nd parent of foo
+                if suffix[i] == '^':
+                    j = i + 1
+                    p = cl.parentrevs(rev)
+                    if j < len(suffix) and suffix[j].isdigit():
+                        j += 1
+                        n = int(suffix[i+1:j])
+                        if n > 2 or n == 2 and p[1] == -1:
+                            raise
+                    else:
+                        n = 1
+                    if n:
+                        rev = p[n - 1]
+                    i = j
+                # foo~N => Nth first grandparent of foo
+                # foo~0 = foo
+                # foo~1 = foo^1 == foo^ == 1st parent of foo
+                # foo~2 = foo^1^1 == foo^^ == 1st parent of 1st parent of foo
+                elif suffix[i] == '~':
+                    j = i + 1
+                    while j < len(suffix) and suffix[j].isdigit():
+                        j += 1
+                    if j == i + 1:
+                        raise
+                    n = int(suffix[i+1:j])
+                    for k in xrange(n):
+                        rev = cl.parentrevs(rev)[0]
+                    i = j
+                else:
+                    raise
+            return cl.node(rev)
+
+    repo.__class__ = parentrevspecrepo