Fix error in tree iterator when popping up trees

There was an error in the tree iterator where it would
delete two tree levels instead of just one when popping
up a tree level.  Unfortunately the test data for the
tree iterator did not have any deep trees with subtrees
in the middle of the tree items, so this problem went
unnoticed.  This contains the 1-line fix plus new test
data and tests that reveal the issue.

src/iterator.c

@@ -121,7 +121,6 @@ static int tree_iterator__advance(
 			break;
 
 		tree_iterator__pop_frame(ti);
-		git_buf_rtruncate_at_char(&ti->path, '/');
 	}
 
 	if (te && entry_is_tree(te))

tests-clar/diff/iterator.c

@@ -139,6 +139,40 @@ void test_diff_iterator__tree_3(void)
 	tree_iterator_test("status", "0017bd4ab1e", 8, expected_tree_3);
 }
 
+/* $ git ls-tree -r --name-only 24fa9a9fc4e202313e24b648087495441dab432b */
+const char *expected_tree_4[] = {
+	"attr0",
+	"attr1",
+	"attr2",
+	"attr3",
+	"binfile",
+	"gitattributes",
+	"macro_bad",
+	"macro_test",
+	"root_test1",
+	"root_test2",
+	"root_test3",
+	"root_test4.txt",
+	"sub/abc",
+	"sub/file",
+	"sub/sub/file",
+	"sub/sub/subsub.txt",
+	"sub/subdir_test1",
+	"sub/subdir_test2.txt",
+	"subdir/.gitattributes",
+	"subdir/abc",
+	"subdir/subdir_test1",
+	"subdir/subdir_test2.txt",
+	"subdir2/subdir2_test1",
+	NULL
+};
+
+void test_diff_iterator__tree_4(void)
+{
+	tree_iterator_test(
+		"attr", "24fa9a9fc4e202313e24b648087495441dab432b",
+		23, expected_tree_4);
+}
 
 /* -- INDEX ITERATOR TESTS -- */
 
@@ -188,6 +222,12 @@ static const char *expected_index_0[] = {
 	"root_test2",
 	"root_test3",
 	"root_test4.txt",
+	"sub/abc",
+	"sub/file",
+	"sub/sub/file",
+	"sub/sub/subsub.txt",
+	"sub/subdir_test1",
+	"sub/subdir_test2.txt",
 	"subdir/.gitattributes",
 	"subdir/abc",
 	"subdir/subdir_test1",
@@ -208,6 +248,12 @@ static const char *expected_index_oids_0[] = {
 	"4d713dc48e6b1bd75b0d61ad078ba9ca3a56745d",
 	"108bb4e7fd7b16490dc33ff7d972151e73d7166e",
 	"fe773770c5a6cc7185580c9204b1ff18a33ff3fc",
+	"3e42ffc54a663f9401cc25843d6c0e71a33e4249",
+	"45b983be36b73c0788dc9cbcb76cbb80fc7bb057",
+	"45b983be36b73c0788dc9cbcb76cbb80fc7bb057",
+	"9e5bdc47d6a80f2be0ea3049ad74231b94609242",
+	"e563cf4758f0d646f1b14b76016aa17fa9e549a4",
+	"fb5067b1aef3ac1ada4b379dbcb7d17255df7d78",
 	"99eae476896f4907224978b88e5ecaa6c5bb67a9",
 	"3e42ffc54a663f9401cc25843d6c0e71a33e4249",
 	"e563cf4758f0d646f1b14b76016aa17fa9e549a4",
@@ -217,7 +263,7 @@ static const char *expected_index_oids_0[] = {
 
 void test_diff_iterator__index_0(void)
 {
-	index_iterator_test("attr", 17, expected_index_0, expected_index_oids_0);
+	index_iterator_test("attr", 23, expected_index_0, expected_index_oids_0);
 }
 
 static const char *expected_index_1[] = {