Conf files should expand env vars (#363)

cmd/backup/config_provider.go

@@ -69,7 +69,11 @@ func loadEnvFiles(directory string) ([]configFile, error) {
 			continue
 		}
 		p := filepath.Join(directory, item.Name())
-		envFile, err := godotenv.Read(p)
+		f, err := os.ReadFile(p)
+		if err != nil {
+			return nil, fmt.Errorf("loadEnvFiles: error reading %s: %w", item.Name(), err)
+		}
+		envFile, err := godotenv.Unmarshal(os.ExpandEnv(string(f)))
 		if err != nil {
 			return nil, fmt.Errorf("loadEnvFiles: error reading config file %s: %w", p, err)
 		}

test/confd/01backup.env

@@ -1,2 +1,2 @@
-NAME="conf"
+NAME="$EXPANSION_VALUE"
 BACKUP_CRON_EXPRESSION="*/1 * * * *"

test/confd/docker-compose.yml

@@ -7,6 +7,7 @@ services:
     environment:
       BACKUP_FILENAME: $$NAME.tar.gz
       BACKUP_FILENAME_EXPAND: 'true'
+      EXPANSION_VALUE: conf
     volumes:
       - ${LOCAL_DIR:-./local}:/archive
       - app_data:/backup/app_data:ro