Improve negative test (#2428)

Author: shadowspawn

lib/command.js

@@ -1756,7 +1756,7 @@ Expecting one of '${allowedValues.join("', '")}'`);
 
     const negativeNumberArg = (arg) => {
       // return false if not a negative number
-      if (!/^-\d*\.?\d+(e[+-]?\d+)?$/.test(arg)) return false;
+      if (!/^-(\d+|\d*\.\d+)(e[+-]?\d+)?$/.test(arg)) return false;
       // negative number is ok unless digit used as an option in command hierarchy
       return !this._getCommandAndAncestors().some((cmd) =>
         cmd.options