commit: refactor option parsing

commit: refactor option parsing

The options are declared as a static global, but really they
need only be accessible from cmd_commit.  Additionally,
declare the "struct wt_status" in cmd_commit and cmd_status
as static at the top of each function; this will let the
options lists reference them directly, which will facilitate
further cleanups.

Signed-off-by: Jeff King <peff@peff.net>