completion: teach remote subcommands to complete options
Git-remote needs to complete remote names, its subcommands, and options
thereof. In addition to the existing subcommand and remote name
completion, do also complete the options
Signed-off-by: Cornelius Weig <cornelius.weig@tngtech.com> Reviewed-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>