completion: bisect: complete log opts for visualize subcommand

completion: bisect: complete log opts for visualize subcommand

Arguments passed to the "visualize" subcommand of git-bisect(1) get
forwarded to git-log(1). It thus supports the same options as git-log(1)
would, but our Bash completion script does not know to handle this.

Make completion of porcelain git-log options and option arguments to the
visualize subcommand work by calling __git_complete_log_opts when the
start of an option to the subcommand is seen (visualize doesn't support
any options besides the git-log options).  Add test.

Signed-off-by: Britton Leo Kerin <britton.kerin@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>