Add bash completion for `--platform`

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

contrib/completion/bash/docker

@@ -1768,6 +1768,9 @@ _docker_container_run_and_create() {
 		--io-maxiops
 		--isolation
 	"
+	__docker_daemon_is_experimental && options_with_args+="
+		--platform
+	"
 
 	local boolean_options="
 		--disable-content-trust=false
@@ -2472,10 +2475,15 @@ _docker_image_build() {
 		--quiet -q
 		--rm
 	"
-	__docker_daemon_is_experimental && boolean_options+="
+	if __docker_daemon_is_experimental ; then
+		options_with_args+="
+			--platform
+		"
+		boolean_options+="
 			--squash
 			--stream
 		"
+	fi
 
 	local all_options="$options_with_args $boolean_options"
 
@@ -2687,12 +2695,21 @@ _docker_image_prune() {
 }
 
 _docker_image_pull() {
+	case "$prev" in
+		--platform)
+			return
+			;;
+	esac
+
 	case "$cur" in
 		-*)
-			COMPREPLY=( $( compgen -W "--all-tags -a --disable-content-trust=false --help" -- "$cur" ) )
+			local options="--all-tags -a --disable-content-trust=false --help"
+			__docker_daemon_is_experimental && options+=" --platform"
+
+			COMPREPLY=( $( compgen -W "$options" -- "$cur" ) )
 			;;
 		*)
-			local counter=$(__docker_pos_first_nonflag)
+			local counter=$(__docker_pos_first_nonflag --platform)
 			if [ "$cword" -eq "$counter" ]; then
 				for arg in "${COMP_WORDS[@]}"; do
 					case "$arg" in