rust: start plugging the dirstate tree behind a feature gate The previous patch added the `dirstate-tree` feature gate to enable the two dirstate implementations to co-habit while the tree-based one gets better. This patch copies over the code that differs, be it because the algorithm changed or because the borrowing rules are different. Indeed, `DirstateTree` is not observationally equivalent to the std `HashMap` in the APIs we use: it does not have the `Entry` API (yet?) and its iterator returns owned values instead of references. This last point is because the implementation needs to be changed to a more clever and efficient solution. Differential Revision: https://phab.mercurial-scm.org/D9133

--- a/rust/hg-cpython/src/dirstate/status.rs	Wed Sep 30 18:10:53 2020 +0200
+++ b/rust/hg-cpython/src/dirstate/status.rs	Wed Sep 30 18:10:29 2020 +0200
@@ -159,7 +159,7 @@
                 .collect();
 
             let files = files?;
-            let matcher = FileMatcher::new(&files)
+            let matcher = FileMatcher::new(files.as_ref())
                 .map_err(|e| PyErr::new::<ValueError, _>(py, e.to_string()))?;
             let ((lookup, status_res), warnings) = status(
                 &dmap,