gh-102950: Adjust tarfile filter tests for systems that don't set the sticky bit (GH-103831)

Also remove expilcit `type=tarfile.DIRTYPE`, the slash at the end is
enough.

Author: encukou

Lib/test/test_tarfile.py

@@ -3635,23 +3635,43 @@ def test_modes(self):
             arc.add('exec_group_other', mode='?rw-rwxrwx')
             arc.add('read_group_only', mode='?---r-----')
             arc.add('no_bits', mode='?---------')
-            arc.add('dir/', mode='?---rwsrwt', type=tarfile.DIRTYPE)
+            arc.add('dir/', mode='?---rwsrwt')
+
+        # On some systems, setting the sticky bit is a no-op.
+        # Check if that's the case.
+        tmp_filename = os.path.join(TEMPDIR, "tmp.file")
+        with open(tmp_filename, 'w'):
+            pass
+        os.chmod(tmp_filename, os.stat(tmp_filename).st_mode | stat.S_ISVTX)
+        have_sticky_files = (os.stat(tmp_filename).st_mode & stat.S_ISVTX)
+        os.unlink(tmp_filename)
+
+        os.mkdir(tmp_filename)
+        os.chmod(tmp_filename, os.stat(tmp_filename).st_mode | stat.S_ISVTX)
+        have_sticky_dirs = (os.stat(tmp_filename).st_mode & stat.S_ISVTX)
+        os.rmdir(tmp_filename)
 
         with self.check_context(arc.open(), 'fully_trusted'):
-            self.expect_file('all_bits', mode='?rwsrwsrwt')
+            if have_sticky_files:
+                self.expect_file('all_bits', mode='?rwsrwsrwt')
+            else:
+                self.expect_file('all_bits', mode='?rwsrwsrwx')
             self.expect_file('perm_bits', mode='?rwxrwxrwx')
             self.expect_file('exec_group_other', mode='?rw-rwxrwx')
             self.expect_file('read_group_only', mode='?---r-----')
             self.expect_file('no_bits', mode='?---------')
-            self.expect_file('dir', type=tarfile.DIRTYPE, mode='?---rwsrwt')
+            if have_sticky_dirs:
+                self.expect_file('dir/', mode='?---rwsrwt')
+            else:
+                self.expect_file('dir/', mode='?---rwsrwx')
 
         with self.check_context(arc.open(), 'tar'):
             self.expect_file('all_bits', mode='?rwxr-xr-x')
             self.expect_file('perm_bits', mode='?rwxr-xr-x')
             self.expect_file('exec_group_other', mode='?rw-r-xr-x')
             self.expect_file('read_group_only', mode='?---r-----')
             self.expect_file('no_bits', mode='?---------')
-            self.expect_file('dir/', type=tarfile.DIRTYPE, mode='?---r-xr-x')
+            self.expect_file('dir/', mode='?---r-xr-x')
 
         with self.check_context(arc.open(), 'data'):
             normal_dir_mode = stat.filemode(stat.S_IMODE(
@@ -3661,7 +3681,7 @@ def test_modes(self):
             self.expect_file('exec_group_other', mode='?rw-r--r--')
             self.expect_file('read_group_only', mode='?rw-r-----')
             self.expect_file('no_bits', mode='?rw-------')
-            self.expect_file('dir/', type=tarfile.DIRTYPE, mode=normal_dir_mode)
+            self.expect_file('dir/', mode=normal_dir_mode)
 
     def test_pipe(self):
         # Test handling of a special file