add help for --cmd option

Author: Tatamo

src/cli/index.ts

@@ -22,6 +22,8 @@ commander
 	.on("--help", () => {
 		console.log("");
 		console.log(help.task_choices);
+		console.log("");
+		console.log(help.cmd_env_variables);
 	});
 
 commander

src/help.ts

@@ -6,6 +6,10 @@ export const task_choices = `Supported arguments for --choice:
            (without --force option, same with "all")
   next     select the top task that is not added yet`;
 
+export const cmd_env_variables = `Environment variables available in --cmd option:
+  $CONTEST_DIR  the path of the contest directory
+  $CONTEST_ID   the contest id`;
+
 export const format_strings = `Supported format strings:
   {TaskLabel}     task label (e.g. A, B, C, D, ...)
   {tasklabel}     task label, lower case