Added a build system based on Robo

RoboFile.php

@@ -0,0 +1,89 @@
+<?php
+declare(strict_types=1);
+use Robo\{Result, Tasks};
+
+// Load the dependencies.
+require_once __DIR__.'/vendor/autoload.php';
+
+/**
+ * Provides tasks for the build system.
+ */
+class RoboFile extends Tasks {
+
+  /**
+   * Creates a new task runner.
+   */
+  function __construct() {
+    $path = (string) getenv('PATH');
+    $vendor = (string) realpath('vendor/bin');
+    if (strpos($path, $vendor) === false) putenv("PATH=$vendor".PATH_SEPARATOR.$path);
+  }
+
+  /**
+   * Deletes all generated files and reset any saved state.
+   */
+  function clean(): void {
+    $this->_cleanDir('var');
+    $this->_deleteDir(['build', 'doc/api', 'web']);
+  }
+
+  /**
+   * Uploads the results of the code coverage.
+   */
+  function coverage(): void {
+    $this->_exec('coveralls var/coverage.xml');
+  }
+
+  /**
+   * Builds the documentation.
+   */
+  function doc(): void {
+    $this->_exec('phpdoc');
+  }
+
+  /**
+   * Performs the static analysis of source code.
+   */
+  function lint(): void {
+    $this->_exec('php -l example/main.php');
+    $this->_exec('phpstan analyse');
+  }
+
+  /**
+   * Runs the test suites.
+   * @return Result The task result.
+   */
+  function test(): Result {
+    return $this->taskPhpUnit()->run();
+  }
+
+  /**
+   * Upgrades the project to the latest revision.
+   */
+  function upgrade(): void {
+    $composer = escapeshellarg(PHP_OS_FAMILY == 'Windows' ? 'C:\Program Files\PHP\share\composer.phar' : '/usr/local/bin/composer');
+    $this->taskExecStack()->stopOnFail()
+      ->exec('git reset --hard')
+      ->exec('git fetch --all --prune')
+      ->exec('git pull --rebase')
+      ->exec("php $composer update --no-interaction")
+      ->run();
+  }
+
+  /**
+   * Increments the version number of the package.
+   * @param string $component The part in the version number to increment.
+   */
+  function version(string $component = 'patch'): void {
+    $this->taskSemVer('.semver')->increment($component)->run();
+  }
+
+  /**
+   * Watches for file changes.
+   */
+  function watch(): void {
+    $this->taskWatch()
+      ->monitor(['lib', 'test'], function() { $this->test(); })
+      ->run();
+  }
+}