Merge branch 'jc/diff-tree-stdin-fix' into maint

"diff-tree --stdin" has been broken for about a year, but 2.36
release broke it even worse by breaking running the command with
<pathspec>, which in turn broke "gitk" and got noticed.  This has
been corrected by aligning its behaviour to that of "log".

This fixes a regression in 2.36 and is slate to go to 2.36.1
source: <xmqq7d7bsu2n.fsf@gitster.g>

* jc/diff-tree-stdin-fix:
  2.36 gitk/diff-tree --stdin regression fix

builtin/diff-tree.c

@@ -195,6 +195,7 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 		int saved_dcctc = 0;
 
 		opt->diffopt.rotate_to_strict = 0;
+		opt->diffopt.no_free = 1;
 		if (opt->diffopt.detect_rename) {
 			if (!the_index.cache)
 				repo_read_index(the_repository);
@@ -217,6 +218,8 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 		}
 		opt->diffopt.degraded_cc_to_c = saved_dcctc;
 		opt->diffopt.needed_rename_limit = saved_nrl;
+		opt->diffopt.no_free = 0;
+		diff_free(&opt->diffopt);
 	}
 
 	return diff_result_code(&opt->diffopt, 0);

log-tree.c

@@ -1098,6 +1098,7 @@ int log_tree_commit(struct rev_info *opt, struct commit *commit)
 	opt->loginfo = &log;
 	opt->diffopt.no_free = 1;
 
+	/* NEEDSWORK: no restoring of no_free?  Why? */
 	if (opt->line_level_traverse)
 		return line_log_print(opt, commit);
 

t/t4013-diff-various.sh

@@ -542,6 +542,20 @@ test_expect_success 'diff-tree --stdin with log formatting' '
 	test_cmp expect actual
 '
 
+test_expect_success 'diff-tree --stdin with pathspec' '
+	cat >expect <<-EOF &&
+	Third
+
+	dir/sub
+	Second
+
+	dir/sub
+	EOF
+	git rev-list master^ |
+	git diff-tree -r --stdin --name-only --format=%s dir >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'diff -I<regex>: setup' '
 	git checkout master &&
 	test_seq 50 >file0 &&