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.
running: init test1
result: 0
running: add foo
result: 0
running: commit -m commit1 -d 2000-01-01 foo
result: 0
running: commit -m commit2 -d 2000-01-02 foo
result: 0
running: log -r 0
changeset: 0:0e4634943879
user: test
date: Sat Jan 01 00:00:00 2000 +0000
summary: commit1
result: 0
running: log -r tip
changeset: 1:45589e459b2e
tag: tip
user: test
date: Sun Jan 02 00:00:00 2000 +0000
summary: commit2
result: 0