There seems to be little reason to return early with an empty list
when there are no subcommands, instead of going through the loop 0
times and then returning the empty list.
Originally, clap carried a lifetime parameter. When moving away from
that, we took the approach that dynamically generated strings are always
supported and `&'static str` was just an optimization.
The problem is the code size increase from this is dramatic. So we're
taking the opposite approach and making dynamic formatting opt-in under
the `string` feature flag. When deciding on an implementation, I
favored the faster one rather than the one with smaller code size since
small code size can be gotten through other means.
Before: 567.2 KiB, 15.975 µs
After: 541.1 KiB, 9.7855 µs
With `string`: 576.6 KiB, 13.016 µs
Adds parser flags to toggle whether to run the
expensive clone logic for completions case.
Help completion will only suggest subcommands, not args.
clap_complete generator sets the flag.
Another step towards #1041
This isn't the long term type for `PossibleValue::help`, I just wanted
to get the lifetime out of the way first before figuring out how help
will work.
`Command::_build_all` started as an internal function for
`clap_complete` as a stopgap until #2911. Overtime, we've been finding
more cases where this function needs to be called, so now we're going to
fully embrace it until #2911 so people aren't scrared off by the hidden
implementation from using it.
This was inspired by #3602
Comptibility: Though this adds a deprecation which we general reserve
for minor or major versions, this is enough of a corner case that I'm
fine doing this in a patch release.
