refactor: unify command declaration across codebase

plugins/ps/subcommands/rebuild

@@ -6,8 +6,10 @@ source "$PLUGIN_AVAILABLE_PATH/ps/functions"
 
 cmd-ps-rebuild() {
   declare desc="rebuilds an app from source"
-  local cmd="ps:rebuild"
-  local APP="$2"
+  declare cmd="ps:rebuild"
+  [[ "$1" == "$cmd" ]] && shift 1
+  declare APP="$1"
+
   [[ -z "$APP" ]] && dokku_log_fail "Please specify an app to run the command on"
 
   if (is_deployed "$APP"); then