Re: [PATCH] reset: Better warning message on git reset --mixed <paths>

Regarding the various modes that are forbidden with "reset", I've been wondering if we can do things differently.

If you want to reset the index at selected paths, don't use any option, as nothing but --mixed makes sense. Hence we deprecated use of --mixed when used this way. But if _it_ makes sense, why deprecate it? What harm would it do if we took it silently?

IIRC, the reasoning that lead to the deprecation was that allowing --mixed may give a false impression to confused users that other mode options also might be usable with pathspec, e.g. "reset --soft [<commit>] <pathspec>". It obviously should barf loudly, as there is no way to move the HEAD to a named commit without touching the index and the worktree at only specified paths, but then the error message belongs to --soft, not --mixed.

Also "reset --hard [<commit>] -- <pathspec>" is forbidden in a repository with a working tree, but it is clear that what the user wanted to do with that unsupported command was what "checkout [<commit>] -- <pathspec>" would have done.

What if we:

 - change "reset --hard [<commit>] -- <pathspec>" to internally run the
   moral equivalent "checkout" without complaining;

 - change "reset --mixed [<commit>] -- <pathspec>" to do the same thing as
   it has always done without complaining; and

 - make sure "reset --soft [<commit>] -- <pathspec>" barfs loudly.

Do people see major downside?