diff rust/hg-core/src/dirstate_tree/dirstate_map.rs @ 47349:7138c863d0a1

dirstate-v2: Skip readdir in status based on directory mtime

When calling `read_dir` during `status` and the directory is found to be
eligible for caching (see code comments), write the directory’s mtime to the
dirstate. The presence of a directory mtime in the dirstate is meaningful
and indicates eligibility.

When an eligible directory mtime is found in the dirstate and `stat()` shows
that the mtime has not changed, `status` can skip calling `read_dir` again
and instead rely on the names of child nodes in the dirstate tree.

The `tempfile` crate is used to create a temporary file in order to use its
modification time as "current time" with the same truncation as other files
and directories would have in their own modification time.

Differential Revision: https://phab.mercurial-scm.org/D10826

--- a/rust/hg-core/src/dirstate_tree/dirstate_map.rs	Thu May 27 18:40:54 2021 +0200
+++ b/rust/hg-core/src/dirstate_tree/dirstate_map.rs	Fri May 28 11:48:59 2021 +0200
@@ -317,6 +317,18 @@
         }
     }
 
+    pub(super) fn cached_directory_mtime(
+        &self,
+    ) -> Option<&on_disk::Timestamp> {
+        match self {
+            NodeRef::InMemory(_path, node) => match &node.data {
+                NodeData::CachedDirectory { mtime } => Some(mtime),
+                _ => None,
+            },
+            NodeRef::OnDisk(node) => node.cached_directory_mtime(),
+        }
+    }
+
     pub(super) fn tracked_descendants_count(&self) -> u32 {
         match self {
             NodeRef::InMemory(_path, node) => node.tracked_descendants_count,
@@ -479,7 +491,7 @@
         }
     }
 
-    fn get_or_insert_node<'tree, 'path>(
+    pub(super) fn get_or_insert_node<'tree, 'path>(
         on_disk: &'on_disk [u8],
         root: &'tree mut ChildNodes<'on_disk>,
         path: &'path HgPath,