Merge branch 'dl/stash-show-untracked-fixup'

The code to handle options recently added to "git stash show"
around untracked part of the stash segfaulted when these options
were used on a stash entry that does not record untracked part.

* dl/stash-show-untracked-fixup:
  stash show: fix segfault with --{include,only}-untracked
  t3905: correct test title

builtin/stash.c

@@ -902,10 +902,14 @@ static int show_stash(int argc, const char **argv, const char *prefix)
 		diff_tree_oid(&info.b_commit, &info.w_commit, "", &rev.diffopt);
 		break;
 	case UNTRACKED_ONLY:
-		diff_root_tree_oid(&info.u_tree, "", &rev.diffopt);
+		if (info.has_u)
+			diff_root_tree_oid(&info.u_tree, "", &rev.diffopt);
 		break;
 	case UNTRACKED_INCLUDE:
-		diff_include_untracked(&info, &rev.diffopt);
+		if (info.has_u)
+			diff_include_untracked(&info, &rev.diffopt);
+		else
+			diff_tree_oid(&info.b_commit, &info.w_commit, "", &rev.diffopt);
 		break;
 	}
 	log_tree_diff_flush(&rev);

t/t3905-stash-include-untracked.sh

@@ -367,7 +367,7 @@ test_expect_success 'stash show --only-untracked only shows untracked files' '
 	test_cmp expect actual
 '
 
-test_expect_success 'stash show --no-include-untracked cancels --{include,show}-untracked' '
+test_expect_success 'stash show --no-include-untracked cancels --{include,only}-untracked' '
 	git reset --hard &&
 	git clean -xf &&
 	>untracked &&
@@ -405,4 +405,19 @@ test_expect_success 'stash show --include-untracked errors on duplicate files' '
 	test_i18ngrep "worktree and untracked commit have duplicate entries: tracked" err
 '
 
+test_expect_success 'stash show --{include,only}-untracked on stashes without untracked entries' '
+	git reset --hard &&
+	git clean -xf &&
+	>tracked &&
+	git add tracked &&
+	git stash &&
+
+	git stash show >expect &&
+	git stash show --include-untracked >actual &&
+	test_cmp expect actual &&
+
+	git stash show --only-untracked >actual &&
+	test_must_be_empty actual
+'
+
 test_done