Improve documentation of supported arguments about pyupgrade

[asottile]

there's no reason to. when you typo'd the tool spit out the answer you were looking for directly and the standard way to ask a tool what it supports is via --help

[WoosterInitiative]

Sure, but when using pre-commit, there may not be a local install to run --help with. Also, the "answer" it provided was less than helpful. Helpful messages I've seen will say things like "'--py312plus' is not a valid argument, valid choices are '--py310-plus', '--py311-plus'" etc., or perhaps point to documentation.

I guess I don't see why this is such a difficult ask. Even if the readme pointed the user to the appropriate file to avoid having to remember to update the readme every time a new option was added, that would help hapless users such as myself, I think.

[asottile]

I've seen will say things like "'--py312plus' is not a valid argument, valid choices are '--py310-plus', '--py311-plus'" etc

that's literally what it does

[WoosterInitiative]

that's literally what it does

Holy balls, man, I missed that somehow. Just tested by intentionally mis-typing it and it does exactly that. Sorry for the trouble!

[asottile]

I'm sure you can see now why I'm frustrated that you wasted both of our time on this