The status command recently grew "short" and "porcelain"
options for alternate output formats. Since status is no
longer "commit --dry-run", these formats are inaccessible to
people who do want to see a dry-run in a parseable form.
This patch makes those formats available to "git commit",
implying the "dry-run" option when they are used.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>