Allow the registration of command aliases to override 'which'

src/Engine/EngineBase.php

@@ -274,6 +274,17 @@ public function shellWhich($command) {
       return $cache[$command];
     }
 
+    // Look at manual aliases.
+    $alias = $this->converter->getCommandAlias($command);
+    if (isset($alias)) {
+      $path = realpath($alias);
+      if ($path === FALSE) {
+        $path = NULL;
+      }
+      $cache[$command] = $path;
+      return $path;
+    }
+
     // Look in the bin folder for FileConverter-provided bins (symlinks work fine).
     $bin = realpath(__DIR__ . '/../../bin/' . $command);
     if ($bin !== FALSE && is_executable($bin)) {

src/FileConverter.php

@@ -40,7 +40,9 @@ static public function &factory($get_singleton = TRUE) {
   }
 
   protected $configurations = array();
-  protected $settings = array();
+  protected $settings = array(
+    'alias' => array(),
+  );
   protected $missing_engines = array();
   protected $previous_engines = array();
   protected $conversion_depth = 0;
@@ -167,6 +169,13 @@ public function convertString($source, &$destination, $convert_path = 'null->nul
     return $this;
   }
 
+  public function getCommandAlias($command) {
+    if (isset($this->settings['alias'][$command])) {
+      return $this->settings['alias'][$command];
+    }
+    return NULL;
+  }
+
   public function getConvertedString($source, $convert_path = 'null->null') {
     $destination = '';
     $this->convertString($source, $destination, $convert_path);
@@ -274,7 +283,7 @@ public function getEngines($convert_path, $configuration_overrides = NULL, $conf
         // This is similar to setConverter('a->b', 'force_id'),
         //   except that it might not be the first engine tried.
         if (isset($configuration['#final'])) {
-          break(2);
+          break (2);
         }
       }
     }
@@ -333,6 +342,10 @@ public function optimizeFile($source = NULL, $destination = NULL, $ext = NULL) {
     return $this->convert('file', "$ext->$ext", $source, $destination);
   }
 
+  public function &setCommandAlias($alias, $path) {
+    $this->settings['alias'][$alias] = $path;
+  }
+
   public function &setConverter($convert_path = 'null->null', $configuration = 'null:default') {
     $conf = new ConfigurationOverride($this->settings);
     $conf->setConverter($convert_path, $configuration);