rust-index: using `hg::index::Index` in `hg-cpython::dagops` Hooking `headrevs` to the Rust index is straightforward as long as we go the `PySharedRef` way. Direct attempts of obtaining a reference to the inner `hg::index::Index` fail for lifetime reasons: the reference is bound to the GIL, yet the `as_set` local variable is considered to be static (the borrow checker clearly does not realize or care that this set only stores `Revision` values). In `rank()`, the chosen solution is the simplest as far as `hg-cpython` is concerned, but it has the defect of removing an implementation that would be easily adaptable if the core index did implement `RankedGraph` (returning the same error as long as only `REVLOGV1` is supported), but that would introduce a direct dependency of `hg-core` on the ``vcsgraph` crate.

--- a/tests/test-rust-ancestor.py	Sat Oct 28 22:50:10 2023 +0200
+++ b/tests/test-rust-ancestor.py	Sun Oct 29 10:47:54 2023 +0100
@@ -157,7 +157,7 @@
         self.assertEqual(exc.args, ('InvalidRevision', wdirrev))
 
     def testheadrevs(self):
-        idx = self.parseindex()
+        idx = self.parserustindex()
         self.assertEqual(dagop.headrevs(idx, [1, 2, 3]), {3})