moved path detection to separate method

Author: rnorth

CHANGELOG.md

@@ -3,7 +3,7 @@ All notable changes to this project will be documented in this file.
 
 ### Fixed
 - Fixed retrieval of Docker host IP when running inside Docker. ([\#479](https://github.com/testcontainers/testcontainers-java/issues/479))
-- Compose can now pull images from private repositories.
+- Compose is now able to pull images from private repositories. ([\#536](https://github.com/testcontainers/testcontainers-java/issues/536))
 - Fixed overriding MySQL image command. ([\#534](https://github.com/testcontainers/testcontainers-java/issues/534))
 
 ### Changed

core/src/main/java/org/testcontainers/containers/DockerComposeContainer.java

@@ -399,18 +399,26 @@ public ContainerisedDockerCompose(List<File> composeFiles, String identifier) {
         setStartupCheckStrategy(new IndefiniteWaitOneShotStartupCheckStrategy());
         setWorkingDirectory(containerPwd);
 
+        String dockerConfigPath = determineDockerConfigPath();
+        if (dockerConfigPath != null && dockerConfigPath.isEmpty()) {
+            addFileSystemBind(dockerConfigPath, DOCKER_CONFIG_FILE, READ_ONLY);
+        }
+    }
+
+    private String determineDockerConfigPath() {
         String dockerConfigEnv = System.getenv(DOCKER_CONFIG_ENV);
         String dockerConfigProperty = System.getProperty(DOCKER_CONFIG_PROPERTY);
         Path dockerConfig = Paths.get(System.getProperty("user.home"), ".docker", "config.json");
 
         if (dockerConfigEnv != null && !dockerConfigEnv.trim().isEmpty() && Files.exists(Paths.get(dockerConfigEnv))) {
-            addFileSystemBind(dockerConfigEnv, DOCKER_CONFIG_FILE, READ_ONLY);
+            return dockerConfigEnv;
         } else if (dockerConfigProperty != null && !dockerConfigProperty.trim().isEmpty() && Files.exists(Paths.get(dockerConfigProperty))) {
-            addFileSystemBind(dockerConfigProperty, DOCKER_CONFIG_FILE, READ_ONLY);
+            return dockerConfigProperty;
         } else if (Files.exists(dockerConfig)) {
-            addFileSystemBind(dockerConfig.toString(), DOCKER_CONFIG_FILE, READ_ONLY);
+            return dockerConfig.toString();
+        } else {
+            return null;
         }
-
     }
 
     private String getDockerSocketHostPath() {