Skip directories with .datmanskip files

datman/src/tree.rs

@@ -316,6 +316,15 @@ pub fn scan_with_progress_bar(
 
         for entry in dir_read? {
             let entry: DirEntry = entry?;
+
+            if entry.file_name() == ".datmanskip" {
+                // Directories with .datmanskip in them are to be skipped entirely.
+                // TODO(perf): should this be checked upfront before some children may already
+                //     have been scanned?
+                debug!("Skipping {path:?} because it has a .datmanskip file.");
+                return Ok(None);
+            }
+
             let scanned =
                 scan_with_progress_bar(&entry.path(), progress_bar, one_filesystem, exclusions)?;
             if let Some(scanned) = scanned {