rust-status: don't trigger dirstate v1 rewrite when only v2 data is changed

The assumption that we need to rewrite (or append to) the dirstate if the
ignore pattern hash has changed or if any cached directory mtimes have changed
is only valid when using dirstate-v2. In dirstate-v1, neither of these things
are written to disk.

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

@@ -31,6 +31,13 b' use crate::StatusOptions;'
 /// anymore) is less than this fraction of the total amount of existing data.
 const ACCEPTABLE_UNREACHABLE_BYTES_RATIO: f32 = 0.5;
 
+#[derive(Debug, PartialEq, Eq)]
+/// Version of the on-disk format
+pub enum DirstateVersion {
+    V1,
+    V2,
+}
+
 pub struct DirstateMap<'on_disk> {
     /// Contents of the `.hg/dirstate` file
     pub(super) on_disk: &'on_disk [u8],
@@ -53,6 +60,8 b" pub struct DirstateMap<'on_disk> {"
     /// Size of the data used to first load this `DirstateMap`. Used in case
     /// we need to write some new metadata, but no new data on disk.
     pub(super) old_data_size: usize,
+
+    pub(super) dirstate_version: DirstateVersion,
 }
 
 /// Using a plain `HgPathBuf` of the full path from the repository root as a
@@ -434,6 +443,7 b" impl<'on_disk> DirstateMap<'on_disk> {"
             ignore_patterns_hash: [0; on_disk::IGNORE_PATTERNS_HASH_LEN],
             unreachable_bytes: 0,
             old_data_size: 0,
+            dirstate_version: DirstateVersion::V1,
         }
     }
 

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

@@ -3,6 +3,7 b''
 //! See `mercurial/helptext/internals/dirstate-v2.txt`
 
 use crate::dirstate::TruncatedTimestamp;
+use crate::dirstate_tree::dirstate_map::DirstateVersion;
 use crate::dirstate_tree::dirstate_map::{self, DirstateMap, NodeRef};
 use crate::dirstate_tree::path_with_basename::WithBasename;
 use crate::errors::HgError;
@@ -276,7 +277,9 b" pub(super) fn read<'on_disk>("
     metadata: &[u8],
 ) -> Result<DirstateMap<'on_disk>, DirstateV2ParseError> {
     if on_disk.is_empty() {
-        return Ok(DirstateMap::empty(on_disk));
+        let mut map = DirstateMap::empty(on_disk);
+        map.dirstate_version = DirstateVersion::V2;
+        return Ok(map);
     }
     let (meta, _) = TreeMetadata::from_bytes(metadata)
         .map_err(|_| DirstateV2ParseError)?;
@@ -291,6 +294,7 b" pub(super) fn read<'on_disk>("
         ignore_patterns_hash: meta.ignore_patterns_hash,
         unreachable_bytes: meta.unreachable_bytes.get(),
         old_data_size: on_disk.len(),
+        dirstate_version: DirstateVersion::V2,
     };
     Ok(dirstate_map)
 }

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

@@ -4,6 +4,7 b' use crate::dirstate::status::StatusPath;'
 use crate::dirstate_tree::dirstate_map::BorrowedPath;
 use crate::dirstate_tree::dirstate_map::ChildNodesRef;
 use crate::dirstate_tree::dirstate_map::DirstateMap;
+use crate::dirstate_tree::dirstate_map::DirstateVersion;
 use crate::dirstate_tree::dirstate_map::NodeData;
 use crate::dirstate_tree::dirstate_map::NodeRef;
 use crate::dirstate_tree::on_disk::DirstateV2ParseError;
@@ -61,16 +62,29 b" pub fn status<'dirstate>("
 
     let (ignore_fn, warnings, patterns_changed): (IgnoreFnType, _, _) =
         if options.list_ignored || options.list_unknown {
-            let mut hasher = Sha1::new();
-            let (ignore_fn, warnings) = get_ignore_function(
-                ignore_files,
-                &root_dir,
-                &mut |pattern_bytes| hasher.update(pattern_bytes),
-            )?;
-            let new_hash = *hasher.finalize().as_ref();
-            let changed = new_hash != dmap.ignore_patterns_hash;
-            dmap.ignore_patterns_hash = new_hash;
-            (ignore_fn, warnings, Some(changed))
+            let (ignore_fn, warnings, changed) = match dmap.dirstate_version {
+                DirstateVersion::V1 => {
+                    let (ignore_fn, warnings) = get_ignore_function(
+                        ignore_files,
+                        &root_dir,
+                        &mut |_pattern_bytes| {},
+                    )?;
+                    (ignore_fn, warnings, None)
+                }
+                DirstateVersion::V2 => {
+                    let mut hasher = Sha1::new();
+                    let (ignore_fn, warnings) = get_ignore_function(
+                        ignore_files,
+                        &root_dir,
+                        &mut |pattern_bytes| hasher.update(pattern_bytes),
+                    )?;
+                    let new_hash = *hasher.finalize().as_ref();
+                    let changed = new_hash != dmap.ignore_patterns_hash;
+                    dmap.ignore_patterns_hash = new_hash;
+                    (ignore_fn, warnings, Some(changed))
+                }
+            };
+            (ignore_fn, warnings, changed)
         } else {
             (Box::new(|&_| true), vec![], None)
         };
@@ -135,7 +149,8 b" pub fn status<'dirstate>("
 
     outcome.dirty = common.ignore_patterns_have_changed == Some(true)
         || !outdated.is_empty()
-        || !new_cachable.is_empty();
+        || (!new_cachable.is_empty()
+            && dmap.dirstate_version == DirstateVersion::V2);
 
     // Remove outdated mtimes before adding new mtimes, in case a given
     // directory is both