git-reset [--mixed] <tree> [--] <paths>...

git-reset [--mixed] <tree> [--] <paths>...

Sometimes it is asked on the list how to revert selected path in
the index from a tree, most often HEAD, without affecting the
files in the working tree.  A similar operation that also
affects the working tree files has been available in the form of
"git checkout <tree> -- <paths>...".

By definition --soft would never affect either the index nor the
working tree files, and --hard is the way to make the working
tree files as close to pristine, so this new option is available
only for the default --mixed case.

Signed-off-by: Junio C Hamano <junkio@cox.net>