Merge pull request #4641 from albers/completion-pull--parallel

Add bash completion for `pull --parallel`

contrib/completion/bash/docker-compose

@@ -341,7 +341,7 @@ _docker_compose_ps() {
 _docker_compose_pull() {
 	case "$cur" in
 		-*)
-			COMPREPLY=( $( compgen -W "--help --ignore-pull-failures" -- "$cur" ) )
+			COMPREPLY=( $( compgen -W "--help --ignore-pull-failures --parallel" -- "$cur" ) )
 			;;
 		*)
 			__docker_compose_services_from_image