Looks like you are using clap v2? Feel free to ping me for help on moving to v3 then v4. I expect the rate of breaking changes to be slowing down and to be smaller in scope (from the users perspective) so now is a good time. Id love to hear how we can make clap better fit cases like this and how we can help in improving the UX of applications.
We're somewhat limited by what version of clap is available in our internal monorepo. We try to keep things reasonably up-to-date though, so I'm sure we'll upgrade at some point.
I believe we actually only use clap for some side binaries, not for the main sl executable. We have a custom parser for that (https://github.com/facebook/sapling/tree/main/eden/scm/lib/c...), to match the preexisting hg parse behavior. Unfortunately I'm not familiar enough with clap or why we didn't go with clap in the first place to say what we would need to use clap for the main binary.
