Move mimetypemapping.json to mimetypemapping.dist.json

This allows users to create their own mapping file to extend our current
mappings. This makes sure that custom mappings are not lost on OC
upgrades.

config/mimetypemapping.dist.json

@@ -3,6 +3,9 @@
 	"_comment2": "The first index in the mime type array is the assumed correct mimetype",
 	"_comment3": "and the second (if present] is a secure alternative",
 
+	"_comment4": "Any changes you make here will be overwritten on an update of ownCloud",
+	"_comment5": "Put any custom mappings in a new file mimetypemapping.json in this directory",
+
 
 	"3gp": ["video/3gpp"],
 	"7z": ["application/x-7z-compressed"],

lib/private/helper.php

@@ -424,8 +424,15 @@ class OC_Helper {
 	 */
 	static public function getMimetypeDetector() {
 		if (!self::$mimetypeDetector) {
-			$file = file_get_contents(OC::$SERVERROOT . '/config/mimetypemapping.json');
-			$mimetypemapping = get_object_vars(json_decode($file));
+			$dist = file_get_contents(OC::$SERVERROOT . '/config/mimetypemapping.dist.json');
+			$mimetypemapping = get_object_vars(json_decode($dist));
+
+			//Check if need to load custom mappings
+			if (file_exists(OC::$SERVERROOT . '/config/mimetypemapping.json')) {
+				$custom = file_get_contents(OC::$SERVERROOT . '/config/mimetypemapping.json');
+				$custom_mapping = get_object_vars(json_decode($custom));
+				$mimetypemapping = array_merge($mimetypemapping, $custom_mapping);
+			}
 
 			self::$mimetypeDetector = new \OC\Files\Type\Detection();
 			self::$mimetypeDetector->registerTypeArray($mimetypemapping);