refs: pseudorefs are no refs

The `is_root_ref()` function will happily clarify a pseudoref as a root
ref, even though pseudorefs are no refs. Next to being wrong, it also
leads to inconsistent behaviour across ref backends: while the "files"
backend accidentally knows to parse those pseudorefs and thus yields
them to the caller, the "reftable" backend won't ever see the pseudoref
at all because they are never stored in the "reftable" backend.

Fix this issue by filtering out pseudorefs in `is_root_ref()`.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

refs.c

@@ -844,6 +844,37 @@ int is_per_worktree_ref(const char *refname)
 	       starts_with(refname, "refs/rewritten/");
 }
 
+static int is_pseudo_ref(const char *refname)
+{
+	/*
+	 * Pseudorefs are refs that have different semantics compared to
+	 * "normal" refs. These refs can thus not be stored in the ref backend,
+	 * but must always be accessed via the filesystem. The following refs
+	 * are pseudorefs:
+	 *
+	 * - FETCH_HEAD may contain multiple object IDs, and each one of them
+	 *   carries additional metadata like where it came from.
+	 *
+	 * - MERGE_HEAD may contain multiple object IDs when merging multiple
+	 *   heads.
+	 *
+	 * Reading, writing or deleting references must consistently go either
+	 * through the filesystem (pseudorefs) or through the reference
+	 * backend (normal ones).
+	 */
+	static const char * const pseudo_refs[] = {
+		"FETCH_HEAD",
+		"MERGE_HEAD",
+	};
+	size_t i;
+
+	for (i = 0; i < ARRAY_SIZE(pseudo_refs); i++)
+		if (!strcmp(refname, pseudo_refs[i]))
+			return 1;
+
+	return 0;
+}
+
 static int is_root_ref_syntax(const char *refname)
 {
 	const char *c;
@@ -868,7 +899,8 @@ int is_root_ref(const char *refname)
 	};
 	size_t i;
 
-	if (!is_root_ref_syntax(refname))
+	if (!is_root_ref_syntax(refname) ||
+	    is_pseudo_ref(refname))
 		return 0;
 
 	if (ends_with(refname, "_HEAD"))
@@ -1856,37 +1888,6 @@ static int refs_read_special_head(struct ref_store *ref_store,
 	return result;
 }
 
-static int is_pseudo_ref(const char *refname)
-{
-	/*
-	 * Pseudorefs are refs that have different semantics compared to
-	 * "normal" refs. These refs can thus not be stored in the ref backend,
-	 * but must always be accessed via the filesystem. The following refs
-	 * are pseudorefs:
-	 *
-	 * - FETCH_HEAD may contain multiple object IDs, and each one of them
-	 *   carries additional metadata like where it came from.
-	 *
-	 * - MERGE_HEAD may contain multiple object IDs when merging multiple
-	 *   heads.
-	 *
-	 * Reading, writing or deleting references must consistently go either
-	 * through the filesystem (pseudorefs) or through the reference
-	 * backend (normal ones).
-	 */
-	static const char * const pseudo_refs[] = {
-		"FETCH_HEAD",
-		"MERGE_HEAD",
-	};
-	size_t i;
-
-	for (i = 0; i < ARRAY_SIZE(pseudo_refs); i++)
-		if (!strcmp(refname, pseudo_refs[i]))
-			return 1;
-
-	return 0;
-}
-
 int refs_read_raw_ref(struct ref_store *ref_store, const char *refname,
 		      struct object_id *oid, struct strbuf *referent,
 		      unsigned int *type, int *failure_errno)

t/t6302-for-each-ref-filter.sh

@@ -52,6 +52,23 @@ test_expect_success '--include-root-refs pattern prints pseudorefs' '
 	test_cmp expect actual
 '
 
+test_expect_success '--include-root-refs pattern does not print special refs' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit initial &&
+		git rev-parse HEAD >.git/MERGE_HEAD &&
+		git for-each-ref --format="%(refname)" --include-root-refs >actual &&
+		cat >expect <<-EOF &&
+		HEAD
+		$(git symbolic-ref HEAD)
+		refs/tags/initial
+		EOF
+		test_cmp expect actual
+	)
+'
+
 test_expect_success '--include-root-refs with other patterns' '
 	cat >expect <<-\EOF &&
 	HEAD