The flags --[no-]diff-merges only make sense for 'git log' and 'git show', so add a new variable __git_log_show_options for options only relevant to these two commands, and add them there. Also add __git_diff_merges_opts and list the accepted values for --diff-merges, and use it in _git_log and _git_show. Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>