new: added access to paths of target and base charm for relation scripts.

bin/compose

@@ -1307,7 +1307,9 @@ _run_service_relation () {
     relation_dir=$(get_relation_data_dir "$charm" "$target_charm" "$relation_name") || return 1
     RELATION_DATA_FILE=$(get_relation_data_file "$charm" "$target_charm" "$relation_name" "$relation_config") || return 1
     export BASE_CHARM_NAME=$charm
+    export BASE_CHARM_PATH=$(charm.get_dir "$charm")
     export TARGET_CHARM_NAME=$target_charm
+    export TARGET_CHARM_PATH=$(charm.get_dir "$target_charm")
     export RELATION_DATA_FILE
     target_errlvl=0
     if [ -z "$target_script_name" ]; then