at some point we might resync with upstream 1.7

Should we keep this dependency at all, since it's only used in rootcling? Perhaps we can instead replace it with optparse.h (not because one is specifically better than the other but because it makes no sense keeping both and having one fewer dependency is desirable)

Edit: I guess the advantage of this is that it handles subcommands (which rootcling needs), so perhaps the better path would be to remove optparse in favor of this? Or maybe the current situation is fine, as long as both libraries do their job.

Edit2: Ah, but subcommands are not actually handled directly by OptionParser.h, it's done via llvm::SubCommand...

Test Results

    23 files      23 suites   3d 13h 29m 28s ⏱️
 3 856 tests  3 855 ✅ 0 💤 1 ❌
78 544 runs  78 542 ✅ 1 💤 1 ❌

For more details on these failures, see this check.

Results for commit f7d3cf3.

Sure, I would vote for dropping this if CLI11 or optparse.h can be used instead