# HG changeset patch
# User Simon Sapin <simon.sapin@octobus.net>
# Date 1639510596 -3600
# Node ID b005d07ded7dc0944d8133bb710436e5a2be62bc
# Parent  3eb3aef6d3bf97519c2b451ed737f8dc184a2c0a
rhg: Skip reading the contents of ambiguous files in some cases

If the size of the file in the working directory does not match the length of
the filelog data, we know its contents will be different and don’t need to
read it.

rhg still decodes the filelog revision, which is not needed in some cases.

Differential Revision: https://phab.mercurial-scm.org/D11910

diff -r 3eb3aef6d3bf -r b005d07ded7d rust/rhg/src/commands/status.rs
--- a/rust/rhg/src/commands/status.rs	Tue Dec 14 19:47:33 2021 +0100
+++ b/rust/rhg/src/commands/status.rs	Tue Dec 14 20:36:36 2021 +0100
@@ -479,11 +479,23 @@
         return Ok(true);
     }
     let filelog = repo.filelog(hg_path)?;
+    let fs_len = fs_metadata.len();
+    // TODO: check `fs_len` here like below, but based on
+    // `RevlogEntry::uncompressed_len` without decompressing the full filelog
+    // contents where possible. This is only valid if the revlog data does not
+    // contain metadata. See how Python’s `revlog.rawsize` calls
+    // `storageutil.filerevisioncopied`.
+    // (Maybe also check for content-modifying flags? See `revlog.size`.)
     let filelog_entry =
         filelog.data_for_node(entry.node_id()?).map_err(|_| {
             HgError::corrupted("filelog missing node from manifest")
         })?;
     let contents_in_p1 = filelog_entry.data()?;
+    if contents_in_p1.len() as u64 != fs_len {
+        // No need to read the file contents:
+        // it cannot be equal if it has a different length.
+        return Ok(true);
+    }
 
     let fs_contents = if is_symlink {
         get_bytes_from_os_string(vfs.read_link(fs_path)?.into_os_string())