I'm developing a command-line tool that has many user options. Some of the options are lists of values. I'd like the program to be able to parse these listed options directly from the command line, and via a file (e.g. --opt=valA,valB and --opt=vals.txt).
Is it preferable to have two separate options for each case, or have the program interpret the arguments at runtime? I've seen programs doing it both ways but I can't decide which is the better design (if there is an objective reason).