dirstate: add test for non-normal set consistency
This adds a test extension to check that the non-normal set contains the
expected entries. It wraps several methods of the dirstate to check that
the non-normal set has the correct values before and after the call. The
extension lives in contrib so that paranoid developers can easily
enable it to make sure that the non-normal set is consistent across more
complex operations than the included tests.
$ hg init
$ echo a > a
$ hg ci -Am t
adding a
$ hg mv a b
$ hg ci -Am t1
$ hg debugrename b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3
$ hg mv b a
$ hg ci -Am t2
$ hg debugrename a
a renamed from b:37d9b5d994eab34eda9c16b195ace52c7b129980
$ hg debugrename --rev 1 b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3