This reverts commits 24cb8b1..d0abb37 from clap-rs/clap#1840
This is part of #16. clap-rs/clap#1840 wasn't the right call but we
don't have time to make the decision now, so instead of having one
option and changing it in 4.0, this reverts back to clap2 behavior.
For those that want the original behavior, you can usxe
`arg.help_heading(Some("FLAGS"))` on your flags. Limitations:
- This will not give you a special sort order
- This will not get a `[FLAGS]` added to usage
For templates, we removed `{unified}` and `{flags}`. To help people
catch these, a debug_assert was added.
I'm unsure but I think there might be a change in behavior in calcuating
when to show `[OPTION]` in usage. The old code only looked at
`required` while flags looked only at arg groups. We now look at both.
Ideally we'd add these in `_build` and remove special casing for
no-groups except in the sort order of groups. I feel like thats best
left for later.
This also reduced the scope of `App`s public API.
`get_*_with_no_heading` seemed a bit specialized to be in the public
API. #2853 looks at splitting it out into its own PR.
BREAKING CHANGE: Multiple
- `UnifiedHelpMessage` removed
- `{flags}` and `{unified}` are removed and will assert when present.
- `get_*_with_no_heading` removed
Fixes#2807
