extract the success/failure logging of the builder to an interface.

PHPCI/BuildLogger.php

@@ -0,0 +1,31 @@
+<?php
+namespace PHPCI;
+
+use Psr\Log\LogLevel;
+
+/**
+ * PHPCI Build Logger
+ */
+interface BuildLogger
+{
+    /**
+     * Add an entry to the build log.
+     * @param string|string[] $message
+     * @param string $level
+     * @param mixed[] $context
+     */
+    public function log($message, $level = LogLevel::INFO, $context = array());
+
+    /**
+     * Add a success-coloured message to the log.
+     * @param string
+     */
+    public function logSuccess($message);
+
+    /**
+     * Add a failure-coloured message to the log.
+     * @param string $message
+     * @param \Exception $exception The exception that caused the error.
+     */
+    public function logFailure($message, \Exception $exception = null);
+}