Implement 'git reset --patch'
This introduces a --patch mode for git-reset. The basic case is
git reset --patch -- [files...]
which acts as the opposite of 'git add --patch -- [files...]': it
offers hunks for *un*staging. Advanced usage is
git reset --patch <revision> -- [files...]
which offers hunks from the diff between the index and <revision> for
forward application to the index. (That is, the basic case is just
<revision> = HEAD.)
Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>