This adds an alias for `--check` that causes it to behave the same as
`--call=check`. This is done using `BoolFunc` to call a function when
the option is seen and to set it to the correct value. This should allow
command line flags like `--check --call=targets` to work correctly (even
though they conflict) by making it so the first invocation sets the
print function to `check` and the second overwrites the first. This is
the expected behavior for these types of boolean flags.
`BoolFunc` itself is part of the standard library flags package, but
never seems to have made it into pflag possibly because it was added in
go 1.21.
https://pkg.go.dev/flag#FlagSet.BoolFunc
Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>
