diff --git a/rust/hg-core/src/revlog/path_encode.rs b/rust/hg-core/src/revlog/path_encode.rs
--- a/rust/hg-core/src/revlog/path_encode.rs
+++ b/rust/hg-core/src/revlog/path_encode.rs
@@ -576,6 +576,7 @@ fn hash_mangle(src: &[u8], sha: &[u8]) -
     if let Some(l) = last_dot {
         dest.write_bytes(&src[l..]);
     }
+    dest.shrink_to_fit();
     dest
 }