Merge branch 'nd/cache-tree-ita' into maint

"git add -N dir/file && git write-tree" produced an incorrect tree
when there are other paths in the same directory that sorts after
"file".

* nd/cache-tree-ita:
  cache-tree: do not generate empty trees as a result of all i-t-a subentries
  cache-tree.c: fix i-t-a entry skipping directory updates sometimes
  test-lib.sh: introduce and use $EMPTY_BLOB
  test-lib.sh: introduce and use $EMPTY_TREE

1 files changed, 11 insertions, 3 deletions

diff --git a/cache-tree.c b/cache-tree.c
index ddf0cc9f9a..f28b1f45a4 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -319,12 +319,13 @@ static int update_one(struct cache_tree *it,
 	i = 0;
 	while (i < entries) {
 		const struct cache_entry *ce = cache[i];
-		struct cache_tree_sub *sub;
+		struct cache_tree_sub *sub = NULL;
 		const char *path, *slash;
 		int pathlen, entlen;
 		const unsigned char *sha1;
 		unsigned mode;
 		int expected_missing = 0;
+		int contains_ita = 0;
 
 		path = ce->name;
 		pathlen = ce_namelen(ce);
@@ -341,7 +342,8 @@ static int update_one(struct cache_tree *it,
 			i += sub->count;
 			sha1 = sub->cache_tree->sha1;
 			mode = S_IFDIR;
-			if (sub->cache_tree->entry_count < 0) {
+			contains_ita = sub->cache_tree->entry_count < 0;
+			if (contains_ita) {
 				to_invalidate = 1;
 				expected_missing = 1;
 			}
@@ -375,11 +377,17 @@ static int update_one(struct cache_tree *it,
 		 * they are not part of generated trees. Invalidate up
 		 * to root to force cache-tree users to read elsewhere.
 		 */
-		if (ce_intent_to_add(ce)) {
+		if (!sub && ce_intent_to_add(ce)) {
 			to_invalidate = 1;
 			continue;
 		}
 
+		/*
+		 * "sub" can be an empty tree if all subentries are i-t-a.
+		 */
+		if (contains_ita && !hashcmp(sha1, EMPTY_TREE_SHA1_BIN))
+			continue;
+
 		strbuf_grow(&buffer, entlen + 100);
 		strbuf_addf(&buffer, "%o %.*s%c", mode, entlen, path + baselen, '\0');
 		strbuf_add(&buffer, sha1, 20);