cmdutil: make checknotesize() work on str-keyed opts Since this patch changes the behavior of the function, I consider it a bonus if the signature also changes so that extensions can detect which version they're dealing with (for the record, I don't have any such extensions). Therefore, I also dropped an unused `ui` argument and renamed the function to use snake_case. Differential Revision: https://phab.mercurial-scm.org/D10859