Try to get all themes to colorize arguments

This is a failed attempt to get option arguments colorized for all
themes by multi-scoping them with variable.other.

It's a failed attempt because it seems those themes that don't color
variable.parameter, it's not that they don't target the scope but that
they set it same as their default foreground color...

I'm committing this because I think the new architecture for declaring
scopes in an anchor and reusing that everywhere can be useful for future
attempts.

I didn't bother to change syntax tests though.

syntaxes/cmd-help.sublime-syntax

@@ -25,6 +25,9 @@ variables:
   allcaps_argument_name: '[:upper:][[:upper:][:digit:]_]*\b'
   relaxed_argument_name: '[:alpha:][[:alnum:]_-]*\b'
 
+### scopes (last scope is matched first)
+  option_argument_scope: &OPTION_ARGUMENT_SCOPE
+    variable.other.option-argument.cmd-help variable.parameter.option-argument.cmd-help
 
 contexts:
   main:
@@ -98,34 +101,34 @@ contexts:
 
   space-after-option:
     - match: '<.*?>'
-      scope: variable.parameter.option-argument.cmd-help
+      scope: *OPTION_ARGUMENT_SCOPE
       set: option-argument-post
     - match: '{{allcaps_argument_name}}\b'
-      scope: variable.parameter.option-argument.cmd-help
+      scope: *OPTION_ARGUMENT_SCOPE
       set: option-argument-post
     - match: '{{relaxed_argument_name}}(?! [:alpha:])'
-      scope: variable.parameter.option-argument.cmd-help
+      scope: *OPTION_ARGUMENT_SCOPE
       set: option-argument-post
     - include: else-pop
 
   equals-after-option:
     - match: '{{relaxed_argument_name}}'
-      scope: variable.parameter.option-argument.cmd-help
+      scope: *OPTION_ARGUMENT_SCOPE
       set: option-argument-post
     - match: '<.*?>'
-      scope: variable.parameter.option-argument.cmd-help
+      scope: *OPTION_ARGUMENT_SCOPE
       set: option-argument-post
     - include: else-pop
 
   square-brackets-after-option:
-    - meta_content_scope: variable.parameter.option-argument.cmd-help
+    - meta_content_scope: *OPTION_ARGUMENT_SCOPE
     - match: '(?=])'
       #fixme: should consume (no lookahead), this forces else-pop on option-argument-post
       set: option-argument-post
 
   option-argument-post:
     - match: '({{ellipsis}})?'
-      scope: variable.parameter.option-argument.cmd-help
+      scope: *OPTION_ARGUMENT_SCOPE
     # - match: ''
     #   set: def-option-post
     - include: connect-option-alias