new: dev: [compose-core] added ``service_base_image_id`` function for charms

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

bin/compose-core

@@ -514,6 +514,19 @@ service_base_image_export_dir() {
 }
 export -f service_base_image_export_dir
 
+
+service_base_image_id() {
+    local service="$1" src="$2" dst="$3" base_image
+    shift
+    base_image=$(service_base_docker_image "$service") || return 1
+    if ! docker_has_image "$base_image"; then
+        docker pull "$base_image"
+    fi
+    docker inspect "$base_image" --format="{{ .Id }}"
+}
+export -f service_base_image_id
+
+
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 ## Generic
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