Add flags and options

[casey]

Recipes should be able to define options:

foo --bar BAZ:
  echo {{BAZ}}

Maybe flags too:

foo --BAZ:
  echo {{BAZ}} # is it "true" or "false"? Or "" or BAZ?

Large changes to the parsing of recipe parameters like this should be considered holistically, along with other possible changes, like $ to support exporting parameters as environment variables, or changing all just variables to being environment variables.

[casey]

It occurs to me that we could use clap to construct recipe argument parsers.

[hustcer]

@casey Will flags be supported ? It's a quite common use case , Thanks !

[hustcer]

flag shorthand can also be supported:
foo --bar(-b):

[sascha-wolf]

Just my two cents: I would already be super happy if I could explicitly refer to the argument's name:

foo bar=something:
	echo {{bar}}

$ just foo bar=stuff
stuff

Of course fully featured flags and options would be lovely but for my personal use-case (and I imagine other's as well) this would already be very helpful, because then I can do things like this:

watch folders='lib,test' cmd='just test':
  find {{ '{' }}{{folders}}{{ '}' }} -name '*.ex*' | entr -dc {{cmd}}

$ just watch cmd='<some other command>'