rust-cpython: raising error.WdirUnsupported
The Graph implementation of hg-cpython returns the appropriate error
upon encounter with the working directory special revision number, and
this gives us in particular a code path to test from test-rust-ancestors.py
In the current implementation, the exception is actually raised from
the iterator instantiation; we are nonetheless consuming the iterator
in the test with `list()` in order not to depend on implementation details.
Ancestors of 5
4 2 0
Ancestors of 6 and 5
4 3 2 1 0
Ancestors of 5 and 4
4 2 0
Ancestors of 7, stop at 6
6
Ancestors of 7, including revs
7 6 5 4 3 2 1 0
Ancestors of 7, 5 and 3, including revs
7 6 5 4 3 2 1 0
Descendants of 5
7 8
Descendants of 5 and 3
6 7 8
Descendants of 5 and 4
5 7 8