refactor(parser): Centralize group handling

Since groups are only associated with the occurrence, we can move the
assigning of it to the occurrence start.

This will help centralize other checks

src/parser/parser.rs

@@ -1078,15 +1078,6 @@ impl<'cmd> Parser<'cmd> {
             matcher.add_index_to(arg.get_id(), self.cur_idx.get());
         }
 
-        // Increment or create the group "args"
-        for group in self.cmd.groups_for_arg(arg.get_id()) {
-            matcher.add_val_to(
-                &group,
-                AnyValue::new(arg.get_id().clone()),
-                OsString::from(arg.get_id().as_str()),
-            );
-        }
-
         Ok(())
     }
 
@@ -1500,7 +1491,12 @@ impl<'cmd> Parser<'cmd> {
         }
         matcher.start_custom_arg(arg, source);
         for group in self.cmd.groups_for_arg(arg.get_id()) {
-            matcher.start_custom_group(group, source);
+            matcher.start_custom_group(group.clone(), source);
+            matcher.add_val_to(
+                &group,
+                AnyValue::new(arg.get_id().clone()),
+                OsString::from(arg.get_id().as_str()),
+            );
         }
     }
 }