Re: [PATCH v4 05/10] unpack-trees: fix nested sparse-dir search

From: Derrick Stolee <redacted>

The iterated search in find_cache_entry() was recently modified to
include a loop that searches backwards for a sparse directory entry that
matches the given traverse_info and name_entry. However, the string
comparison failed to actually concatenate those two strings, so this
failed to find a sparse directory when it was not a top-level directory.

This caused some errors in rare cases where a 'git checkout' spanned a
diff that modified files within the sparse directory entry, but we could
not correctly find the entry.

Helped-by: Johannes Schindelin [off-list ref]
Helped-by: René Scharfe [off-list ref]
Signed-off-by: Derrick Stolee <redacted>
---
 unpack-trees.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/unpack-trees.c b/unpack-trees.c
index 5786645f315..47ef0cf4c53 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c

@@ -1255,7 +1255,8 @@ static int sparse_dir_matches_path(const struct cache_entry *ce,
 static struct cache_entry *find_cache_entry(struct traverse_info *info,
 					    const struct name_entry *p)
 {
-	struct cache_entry *ce;
+	const char *path;
+	struct cache_entry *ce = NULL;

 	int pos = find_cache_pos(info, p->path, p->pathlen);
 	struct unpack_trees_options *o = info->data;

@@ -1283,7 +1284,9 @@ static struct cache_entry *find_cache_entry(struct traverse_info *info,
 	while (pos >= 0) {
 		ce = o->src_index->cache[pos];

-		if (strncmp(ce->name, p->path, p->pathlen))
+		if (!skip_prefix(ce->name, info->traverse_path, &path) ||
+		    strncmp(path, p->path, p->pathlen) ||
+		    path[p->pathlen] != '/')
 			return NULL;

 		if (S_ISSPARSEDIR(ce->ce_mode) &&