Add bash completion for docker build --cache-from

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

contrib/completion/bash/docker

@@ -1901,6 +1901,7 @@ _docker_image() {
 _docker_image_build() {
 	local options_with_args="
 		--build-arg
+		--cache-from
 		--cgroup-parent
 		--cpuset-cpus
 		--cpuset-mems
@@ -1936,6 +1937,10 @@ _docker_image_build() {
 			__docker_nospace
 			return
 			;;
+		--cache-from)
+			__docker_complete_image_repos_and_tags
+			return
+			;;
 		--file|-f)
 			_filedir
 			return