Add --quiet option to suppress STDOUT output

we want to suppress any output that is not an error when running
pdepend. For this I am adding a new option --quiet to the TextUI
Command. Setting this flag will put pdepend into silent mode, meaning it
will use the NulLResultPrinter instead of the regular ResultPrinter and
it will not output version, workarounds and runtime statistics. It will
output any errors though.

Closes #211

src/main/php/PDepend/TextUI/Command.php

@@ -210,6 +210,16 @@ public function run()
             unset($options['--optimization']);
         }
 
+        if (isset($options['--quiet'])) {
+            $runSilent = true;
+            $processListener = new \PDepend\TextUI\NullResultPrinter();
+            unset($options['--quiet']);
+        } else {
+            $runSilent = false;
+            $processListener = new \PDepend\TextUI\ResultPrinter();
+        }
+        $this->runner->addProcessListener($processListener);
+
         if (isset($options['--notify-me'])) {
             $this->runner->addProcessListener(
                 new \PDepend\DbusUI\ResultPrinter()
@@ -225,8 +235,10 @@ public function run()
 
         try {
             // Output current pdepend version and author
-            $this->printVersion();
-            $this->printWorkarounds();
+            if ($runSilent === false) {
+                $this->printVersion();
+                $this->printWorkarounds();
+            }
 
             $startTime = time();
 
@@ -247,8 +259,9 @@ public function run()
                 }
                 echo PHP_EOL;
             }
-
-            $this->printStatistics($startTime);
+            if ($runSilent === false) {
+                $this->printStatistics($startTime);
+            }
 
             return $result;
         } catch (\RuntimeException $e) {
@@ -472,6 +485,7 @@ protected function printHelp()
         );
         echo PHP_EOL;
 
+        $this->printOption('--quiet', 'Prints errors only.', $length);
         $this->printOption('--debug', 'Prints debugging information.', $length);
         $this->printOption('--help', 'Print this help text.', $length);
         $this->printOption('--version', 'Print the current version.', $length);

src/main/resources/services.xml

@@ -8,10 +8,6 @@
         <service id="pdepend.textui.runner" class="PDepend\TextUI\Runner">
             <argument type="service" id="pdepend.report_generator_factory" />
             <argument type="service" id="pdepend.engine" />
-
-            <call method="addProcessListener">
-                <argument type="service" id="pdepend.textui.result_printer" />
-            </call>
         </service>
 
         <service id="pdepend.util.cache_factory" class="PDepend\Util\Cache\CacheFactory">

src/test/php/PDepend/TextUI/CommandTest.php

@@ -543,6 +543,22 @@ public function testCommandFailsIfAnInvalidConfigFileWasSpecified()
         );
     }
 
+    public function testQuietModeWillSuppressVersionAndWorkaroundsAndStatistics()
+    {
+        $argv = array(
+            '--quiet',
+            '--coverage-report=' . dirname(__FILE__) . '/_files/clover.xml',
+            '--dummy-logger=' . $this->createRunResourceURI(),
+            '--configuration=' . __DIR__ . '/../../../resources/pdepend.xml.dist',
+            __FILE__,
+        );
+
+        list($exitCode, $actual) = $this->executeCommand($argv);
+
+        $this->assertEquals(Runner::SUCCESS_EXIT, $exitCode);
+        $this->assertEmpty('', $actual);
+    }
+
     /**
      * Tests the help output with an optional prolog text.
      *
@@ -565,6 +581,7 @@ protected function assertHelpOutput($actual, $prologText = '')
         $this->assertRegExp('(  --help[ ]+Print\s+this\s+help\s+text\.)', $actual);
         $this->assertRegExp('(  --version[ ]+Print\s+the\s+current\s+version\.)', $actual);
         $this->assertRegExp('(  -d key\[=value\][ ]+Sets\s+a\s+php.ini\s+value\.)', $actual);
+        $this->assertRegExp('(  --quiet[ ]+Prints\s+errors\s+only\.)', $actual);
     }
 
     /**