new: support of ``docker-compose.yml`` v2.0

bin/compose

@@ -811,7 +811,21 @@ get_docker_compose () {
         debug "    ..finished all mixins for $DARKYELLOW$target_service$NORMAL $GRAY(in $((SECONDS - start))s)$NORMAL"
     done
 
-    merge_yaml_str "${entries[@]}" > "$cache_file"
+    docker_compose_services=$(merge_yaml_str "${entries[@]}") || return 1
+
+    base_v2="version: '2.0'
+networks:
+  static:
+    driver: bridge
+    ipam:
+      driver: default
+      config:
+      - subnet: 172.25.1.0/24
+
+"
+    merge_yaml_str "$(yaml_key_val_str "services" "$docker_compose_services")" \
+                   "$base_v2" > "$cache_file" || return 1
+
     export _current_docker_compose="$(cat "$cache_file")"
     echo "$_current_docker_compose"
     debug "  ..compilation of base 'docker-compose.yml' done $GRAY(in $((SECONDS - start_compilation))s)$NORMAL" || true
@@ -897,7 +911,7 @@ get_service_def () {
                            "\$_current_docker_compose has been calculated."
     fi
 
-    def=$(echo "$_current_docker_compose" | shyaml get-value "$service" 2>/dev/null)
+    def=$(echo "$_current_docker_compose" | shyaml get-value "services.$service" 2>/dev/null)
     if [ -z "$def" ]; then
         err "No definition for service $DARKYELLOW$service$NORMAL in compiled 'docker-compose.yml'."
         return 1
@@ -1273,7 +1287,8 @@ export -f config-add
 ## XXXvlab; this can be used only in relation, I'd like to use it in init.
 init-config-add() {
     local metadata="$1"
-    _config_merge "$state_tmpdir/to-merge-in-docker-compose.yml" <(echo "$metadata")
+    _config_merge "$state_tmpdir/to-merge-in-docker-compose.yml" \
+                  <(yaml_key_val_str "services" "$metadata")
 }
 export -f init-config-add
 
@@ -1862,9 +1877,13 @@ _get_docker_compose_mixin_from_metadata_cached() {
             mixin=$(echo -en "volumes:\n$volumes")
         fi
 
-        docker_compose=$(echo "$metadata" | shyaml get-value "docker-compose" 2>/dev/null)
+        docker_compose=$(echo "$metadata" | shyaml get-value -y "docker-compose" 2>/dev/null)
         if [ "$docker_compose" ]; then
-            mixin=$(merge_yaml_str "$mixin" "$docker_compose")
+            mixin=$(merge_yaml_str "$mixin" "$docker_compose") || {
+                err "Failed to merge mixin with ${WHITE}docker-compose${NORMAL} option" \
+                    "from charm ${DARKYELLOW}$charm$NORMAL."
+                return 1
+            }
         fi
 
         if [ "$(echo "$metadata" | shyaml get-value "subordinate" 2>/dev/null)" == "True" ]; then
@@ -1960,7 +1979,7 @@ launch_docker_compose() {
     fi
 
     ## XXXvlab: could be more specific and only link the needed charms
-    for charm in $(shyaml keys < "$docker_compose_dir/docker-compose.yml"); do
+    for charm in $(shyaml keys services < "$docker_compose_dir/docker-compose.yml"); do
         if charm.exists "$charm"; then
             ln -sf "$(charm.get_dir "$charm")" "$docker_compose_dir/$charm" || exit 1
         fi