3 Used in when checking for reverts when the checksum of the revision of interest
4 is unknown. DummyChecksums won't match eachother or anything else, but they
5 will match themselves and they are hashable.
7 >>> dummy1 = DummyChecksum()
13 >>> dummy2 = DummyChecksum()
19 >>> {"foo", "bar", dummy1, dummy1, dummy2}
20 {<#140687347334280>, 'foo', <#140687347334504>, 'bar'}
23 def __str__(self): repr(self)
24 def __repr__(self): return "<#" + str(id(self)) + ">"