Instead of maintaining a local variable for it, use s->fp to keep
track of where the commit message template should be written.
This prepares us to take advantage of the status_printf functions,
which use a struct wt_status instead of a FILE pointer to determine
where to send their output.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>