[PATCH v5 3/9] unpack-trees: fix nested sparse-dir search

["Derrick Stolee via GitGitGadget" <gitgitgadget@xxxxxxxxx>]

From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>

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 <Johannes.Schindelin@xxxxxx>
Helped-by: René Scharfe <l.s.r@xxxxxx>
Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
---
 unpack-trees.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/unpack-trees.c b/unpack-trees.c
index 5786645f315..b78d7ee6c09 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -1255,7 +1255,7 @@ 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;
 	int pos = find_cache_pos(info, p->path, p->pathlen);
 	struct unpack_trees_options *o = info->data;
 
@@ -1281,9 +1281,11 @@ static struct cache_entry *find_cache_entry(struct traverse_info *info,
 	 * paths (e.g. "subdir-").
 	 */
 	while (pos >= 0) {
-		ce = o->src_index->cache[pos];
+		struct cache_entry *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) &&
-- 
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