Restore the manifest size doubling when incrementally regenerating one

It turns out this has a huge performance impact.
glandium · Nov 21, 2023 · ec0337c · ec0337c
1 parent 59a5482
commit ec0337c
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/src/store.rs b/src/store.rs
@@ -695,7 +695,8 @@ impl RawHgManifest {
                     cache.set(Some(last_manifest));
                     return RawHgManifest(reference_manifest);
                 }
-                manifest.reserve(reference_manifest.len());
+                // Generously reserve memory for the new manifest to avoid reallocs.
+                manifest.reserve(reference_manifest.len() * 2);
                 // TODO: ideally, we'd be able to use merge_join_by_path, but WithPath
                 // using an owned string has a huge impact on performance.
                 for entry in itertools::merge_join_by(