-perm: Use +t instead of ug+t

The chmod spec says that ug+t is unspecified, and only +t or a+t is
guaranteed to actually set the sticky bit.  In practice GNU tools
respect o+t as well, but ignore u+t/g+t.

Fix the implementation to match GNU, and only test the POSIX required
parse.

2 files changed, 5 insertions, 3 deletions

diff --git a/parse.c b/parse.c
index 4e326ec..fa95e69 100644
--- a/parse.c
+++ b/parse.c
@@ -1896,8 +1896,10 @@ static int parse_mode(const struct parser_state *state, const char *mode, struct
 				}
 				break;
 			case 't':
-				file_change |= S_ISVTX;
-				dir_change |= S_ISVTX;
+				if (who & 0007) {
+					file_change |= S_ISVTX;
+					dir_change |= S_ISVTX;
+				}
 				break;
 			default:
 				mstate = MODE_ACTION_APPLY;
diff --git a/tests.sh b/tests.sh
index 0e1a964..8ec983f 100755
--- a/tests.sh
+++ b/tests.sh
@@ -1762,7 +1762,7 @@ function test_perm_setid() {
 }
 
 function test_perm_sticky() {
-    bfs_diff rainbow -perm /ug+t
+    bfs_diff rainbow -perm /+t
 }
 
 function test_prune() {