Allow use of names for positional-args

[ross-spencer]

Current behavior is to use numbered args in a justfile:

set positional-arguments

@foo bar:
  echo $0
  echo $1

Given bar is labelled and just will report on it if it is missing from the recipe, some syntactic sugar might allow for it to be referenced by name in the recipe, e.g:

set positional-arguments

@foo bar:
  echo $0
  echo $bar

It might just reduce the learning curve of the format a little more for new users but also help make the recipe more reliable if that value need be repeated on any other lines without having to keep in mind the enumeration.

[laniakea64]

set positional-arguments does not prevent the use of just variables -

set positional-arguments

@foo bar:
  echo $0
  echo {{bar}}

[ross-spencer]

set positional-arguments does not prevent the use of just variables

ah, cool. Much nicer.

Feels like there's some skew in definition here between arg/variable but probably not worth going into.

Thanks for pointing that out!