fixes problem where drush_make fails with recursive make files

drush_make.download.inc

@@ -2,6 +2,15 @@
 // $Id$
 
 function drush_make_download_factory($name, $download, $download_location) {
+  // create a check for multiple downloads of the same type
+  static $seen;
+  $seen[$name][] = $download['type'];
+  if (count($seen[$name]) > 1 {
+    drush_log(dt('Attempt to download project %name more than once (%types) prevented',
+      array('%name' => $name, '%types' => join(", ", $seen[$name]))), 'warning');
+    return FALSE;
+  }
+
   $function = 'drush_make_download_' . $download['type'];
   if (function_exists($function)) {
     return $function($name, $download, $download_location);

drush_make.project.inc

@@ -43,16 +43,19 @@ class DrushMakeProject {
   }
 
   function findDownloadLocation() {
+    // setup a way to track where we've already been
+    static $seen;
     $this->path = $this->generatePath();
     $this->project_directory = !empty($this->directory_name) ? $this->directory_name : $this->name;
     $this->download_location = $this->path . '/' . $this->project_directory;
-    // This directory shouldn't exist yet -- if it does, stop.
+    // This directory shouldn't exist yet -- unless a recursively called makefile
+    // re-defines or duplicates a dependency -- in which case we continue and log a warning.
     if (is_dir($this->download_location)) {
-      drush_set_error(dt('Directory not empty: %directory', array('%directory' => $this->download_location)));
-      return FALSE;
+      drush_log(dt('Directory not empty: %directory', array('%directory' => $this->download_location)), "warning");
     }
     else {
       drush_make_mkdir($this->download_location);
+      $seen[$this->download_location] = TRUE;
     }
     return $this->download_location;
   }