Improve bash completion for `docker network disconnect`

Signed-off-by: Harald Albers <github@albersweb.de>

contrib/completion/bash/docker

@@ -157,6 +157,11 @@ __docker_networks() {
 	COMPREPLY=( $(compgen -W "$networks" -- "$cur") )
 }
 
+__docker_containers_in_network() {
+	local containers=$(__docker_q network inspect -f '{{range $i, $c := .Containers}}{{$i}} {{$c.Name}} {{end}}' "$1")
+	COMPREPLY=( $(compgen -W "$containers" -- "$cur") )
+}
+
 __docker_volumes() {
 	COMPREPLY=( $(compgen -W "$(__docker_q volume ls -q)" -- "$cur") )
 }
@@ -1092,7 +1097,7 @@ _docker_network_connect() {
 			COMPREPLY=( $( compgen -W "--help" -- "$cur" ) )
 			;;
 		*)
-			local counter=$(__docker_pos_first_nonflag '--tail')
+			local counter=$(__docker_pos_first_nonflag)
 			if [ $cword -eq $counter ]; then
 				__docker_networks
 			elif [ $cword -eq $(($counter + 1)) ]; then
@@ -1127,9 +1132,19 @@ _docker_network_create() {
 }
 
 _docker_network_disconnect() {
-	# TODO disconnect should only complete running containers connected
-	# to the specified network.
-	_docker_network_connect
+	case "$cur" in
+		-*)
+			COMPREPLY=( $( compgen -W "--help" -- "$cur" ) )
+			;;
+		*)
+			local counter=$(__docker_pos_first_nonflag)
+			if [ $cword -eq $counter ]; then
+				__docker_networks
+			elif [ $cword -eq $(($counter + 1)) ]; then
+				__docker_containers_in_network "$prev"
+			fi
+			;;
+	esac
 }
 
 _docker_network_inspect() {