update-index (bugfix): --cacheinfo should block directories

Add explicit check for directory entry mode, throwing an error if found.
Without the check, sparse directory cache entries could be added to any
index (including non-sparse). In a sparse index, this would at least cause
inconsistencies in the cache tree; for a non-sparse index, such an entry
being present at all is a bug.

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

builtin/update-index.c

@@ -411,6 +411,9 @@ static int add_cacheinfo(unsigned int mode, const struct object_id *oid,
 	if (!verify_path(path, mode))
 		return error("Invalid path '%s'", path);
 
+	if (S_ISSPARSEDIR(mode))
+		return error("%s: cannot add directory as cache entry", path);
+
 	len = strlen(path);
 	ce = make_empty_cache_entry(&the_index, len);
 

t/t2107-update-index-basic.sh

@@ -64,6 +64,14 @@ test_expect_success '--cacheinfo mode,sha1,path (new syntax)' '
 	test_cmp expect actual
 '
 
+test_expect_success '--cacheinfo does not accept directory mode' '
+	mkdir folder1 &&
+	echo content >folder1/content &&
+	git add folder1 &&
+	folder1_oid=$(git ls-files -s folder1 | git hash-object --stdin) &&
+	test_must_fail git update-index --add --cacheinfo 040000 $folder1_oid folder1/
+'
+
 test_expect_success '.lock files cleaned up' '
 	mkdir cleanup &&
 	(