Package commandline contains helper types for collecting command-line arguments.
A ReplaceRule maps a pattern to its replacement. On the command line, ReplaceRules are provided as strings separated by "->".
A ReplaceRuleList is used to collect multiple replacement rules from the command line.
Set adds a replacement rule to the ReplaceRuleList, in the order provided on the command line.
The Strings type can be used to collect multiple command-line options, in the order provided.