git-reset.txt: better docs for '--patch'
git-reset.txt: better docs for '--patch'

Describe '-p' as a short form of '--patch' in synopsis. Also include a better
explanation of this option and additionally refer the reader to the patch mode
description of git-add documentation.

Helped-by: Jeff King <696e3fbcf235d40b6ea1ebd61c87cbea79d444e7@peff.net>
Mentored-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>
Signed-off-by: Valentin Haenel <30f4cb0cdf514d433d42cd7ee92836d84565df20@gmx.de>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git