early stop args

[jmbarbone]

Include parameters that stop the parsing of additional further arguments.

# use default values
ca <- command_args(c("--bar", 2))
ca$add_argument("--bar", default = 1)
ca$add_argument("--foo", action = "flag", stop = "soft") # or TRUE
ca$parse()
#> $bar
#> [1] 1
#> $foo
#> [1] TRUE

# strip out other values
ca <- command_args(c("--bar", 2))
ca$add_argument("--bar", default = 1)
ca$add_argument("--foo", action = "flag", stop = "hard")
ca$parse()
#> $foo
#> [1] TRUE