chmod: Fix file completion after modes starting with a dash

completions/chmod

@@ -17,7 +17,10 @@ _chmod()
 
     $split && return
 
-    if [[ $cur == -* ]]; then
+    # Adapted from coreutils 8.28 chmod man page
+    local modearg="-@(+(*([rwxXst])|[ugo])|+([0-7]))"
+
+    if [[ $cur == -* && $cur != $modearg ]]; then
         local opts=$( _parse_help "$1" )
         [[ $opts ]] || opts=$( _parse_usage "$1" )
         COMPREPLY=( $( compgen -W "$opts" -- "$cur" ) )
@@ -26,7 +29,7 @@ _chmod()
     fi
 
     local args
-    _count_args
+    _count_args "" "" "$modearg"
 
     case $args in
         1) ;;  # mode

test/t/test_chmod.py

@@ -15,3 +15,11 @@ def test_2(self, completion):
     @pytest.mark.complete("chmod -")
     def test_3(self, completion):
         assert completion.list
+
+    @pytest.mark.complete("chmod -x ")
+    def test_4(self, completion):
+        assert completion.list
+
+    @pytest.mark.complete("chmod -77 ")
+    def test_5(self, completion):
+        assert completion.list