clang-format in usage()

[Lestropie]

On having to edit the contents of a command's usage() function for the first time following merge of #2652, I'm immediately repulsed by the formatting of particularly OPTIONS. It's become much harder to navigate.

One prospect that I don't recall discussing in the relevant threads was to simply explicitly disable clang-format via code comments (eg).

Alternatively we can try to find a different syntax that plays better with clang-format; but that would likely lead to a hard backward compatibility break.

[daljit46]

Yes, I think using // clang-format off and // clang-format on to achieve a custom style for a particular piece of code would be the most appropriate.