Add dry-run option to baseplate-script

[pacejackson]

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[pacejackson]

👓 @spladug

How do you feel about this way of communicating dry-run vs live mode? Personally, I would like to make dry-run an argument that get's passed to the function baseplate-script calls but then anyone using this functionality would have to update their scripts to accept it.

[spladug]

I'm not against modifying the signature of the function to be called; we're still in semi-unstable mode here and baseplate-script isn't used heavily much. However, I think this particular flag is probably too specific to certain scripts since not everything needs a dry run flag.

Instead, it hints at a general need to allow scripts to parse their own arguments; would we add another argument to baseplate-script when we want to pass e.g. hostname?

As an alternative, what about making load_and_run_script do ArgumentParser.parse_known_args and then altering the expected script function's signature to take the remaining arguments as a parameter? The called script can ignore them or run its own argument parser on them if desired. This does have the downside that --help won't carry any of the script's own argument parsing info AFAIK, but I'm not sure if there's something better since it seems difficult to parse arguments, find the script to run, load it, let it modify the argument parser, then parse arguments again.

💅