dirstate: fix the bug in [status] dealing with committed&ignored directories

In particular, these directories can "infect" their sibling directories with
ignored status due to using a shared memoization cell by accident.

This fixes bug  #6795.

rust/hg-core/src/dirstate_tree/status.rs

@@ -244,7 +244,7 b" impl<'a> HasIgnoredAncestor<'a> {"
         match self.parent {
             None => false,
             Some(parent) => {
-                *(parent.cache.get_or_init(|| {
+                *(self.cache.get_or_init(|| {
                     parent.force(ignore_fn) || ignore_fn(self.path)
                 }))
             }

tests/test-status-committed-and-ignored.t

@@ -30,6 +30,4 b' Untracked files in d2 are still shown, b'
   $ touch d1/g
   $ touch d2/g
   $ RAYON_NUM_THREADS=1 hg status
-  ? d2/g (no-rust no-rhg !)
-
-^ BUG: d2/g does not show up with rust status
+  ? d2/g