don't move file into subdirectory if a file with the same name already exists (fixes #92)

apps/files/ajax/move.php

@@ -12,6 +12,11 @@ $file = stripslashes($_GET["file"]);
 $target = stripslashes(urldecode($_GET["target"]));
 
 
+if(OC_Filesystem::file_exists($target . '/' . $file)){
+	OCP\JSON::error(array("data" => array( "message" => "Could not move $file - File with this name already exists" )));
+	exit;
+}
+
 if(OC_Files::move($dir, $file, $target, $file)) {
 	OCP\JSON::success(array("data" => array( "dir" => $dir, "files" => $file )));
 } else {