List direct files only for ref name prefix

Previously, `refs/heads/foo/bar` would be listed when running
`repo.references()?.prefixed("refs/heads/b")`. The code identified that
the last component was not a directory and started to match it as a
filename prefix for all files in all recursive directories, effectively
matching `refs/heads/**/b*`.

This commit makes sure to only list direct files and not walk the
directory tree recursively.

Fixes GitoxideLabs#1934.

Author: moroten

gix-ref/src/store/file/loose/iter.rs

@@ -14,17 +14,22 @@ pub(in crate::store_impl::file) struct SortedLoosePaths {
 
 impl SortedLoosePaths {
     pub fn at(path: &Path, base: PathBuf, filename_prefix: Option<BString>, precompose_unicode: bool) -> Self {
+        let has_filename_prefix = filename_prefix.is_some();
         SortedLoosePaths {
             base,
             filename_prefix,
             file_walk: path.is_dir().then(|| {
                 // serial iteration as we expect most refs in packed-refs anyway.
-                gix_features::fs::walkdir_sorted_new(
+                let mut walkdir = gix_features::fs::walkdir_sorted_new(
                     path,
                     gix_features::fs::walkdir::Parallelism::Serial,
                     precompose_unicode,
-                )
-                .into_iter()
+                );
+                // With a filename prefix, only files within the base are of interest.
+                if has_filename_prefix {
+                    walkdir = walkdir.max_depth(1);
+                }
+                walkdir.into_iter()
             }),
         }
     }

gix-ref/tests/fixtures/make_ref_repository.sh

@@ -22,6 +22,11 @@ echo "ref: refs/tags/multi-link-target2" > .git/refs/heads/multi-link-target1
 echo "ref: refs/remotes/origin/multi-link-target3" > .git/refs/tags/multi-link-target2
 git rev-parse HEAD > .git/refs/remotes/origin/multi-link-target3
 
+# Regression test for issue #1934 where prefix refs/m matched refs/heads/main.
+# Testing both single subdirectory with 'sub-dir'.
+mkdir .git/refs/heads/sub-dir
+echo "ref: refs/remotes/origin/main" > .git/refs/heads/sub-dir/d2
+echo "ref: refs/remotes/origin/main" > .git/refs/remotes/origin/heads
 
 echo "ref: refs/loop-b" > .git/refs/loop-a
 echo "ref: refs/loop-a" > .git/refs/loop-b

gix-ref/tests/refs/file/store/iter.rs

@@ -262,7 +262,7 @@ fn loose_iter_with_broken_refs() -> crate::Result {
     let store = store()?;
 
     let mut actual: Vec<_> = store.loose_iter()?.collect();
-    assert_eq!(actual.len(), 16);
+    assert_eq!(actual.len(), 18);
     actual.sort_by_key(Result::is_err);
     let first_error = actual
         .iter()
@@ -271,7 +271,7 @@ fn loose_iter_with_broken_refs() -> crate::Result {
         .expect("there is an error");
 
     assert_eq!(
-        first_error, 15,
+        first_error, 17,
         "there is exactly one invalid item, and it didn't abort the iterator most importantly"
     );
     #[cfg(not(windows))]
@@ -296,10 +296,12 @@ fn loose_iter_with_broken_refs() -> crate::Result {
             "heads/dt1",
             "heads/main",
             "heads/multi-link-target1",
+            "heads/sub-dir/d2",
             "loop-a",
             "loop-b",
             "multi-link",
             "remotes/origin/HEAD",
+            "remotes/origin/heads",
             "remotes/origin/main",
             "remotes/origin/multi-link-target3",
             "tags/dt1",
@@ -349,6 +351,7 @@ fn loose_iter_with_prefix() -> crate::Result {
             "refs/heads/dt1",
             "refs/heads/main",
             "refs/heads/multi-link-target1",
+            "refs/heads/sub-dir/d2",
         ]
         .into_iter()
         .map(String::from)