gui: Keep short deviceID length consistent + xrefs (fixes #9313) (#9314)

Making short deviceID length consistent and referencing to protocol file
for future-proof edits. Closes #9313.

gui/default/syncthing/app.js

@@ -18,6 +18,9 @@ var syncthing = angular.module('syncthing', [
 var urlbase = 'rest';
 var authUrlbase = urlbase + '/noauth/auth';
 
+// keep consistent with ShortIDStringLength in lib/protocol/deviceid.go
+var shortIDStringLength = 7;
+
 syncthing.config(function ($httpProvider, $translateProvider, LocaleServiceProvider) {
     // language and localisation
 

gui/default/syncthing/core/syncthingController.js

@@ -1460,7 +1460,7 @@ angular.module('syncthing.core')
 
         $scope.friendlyNameFromShort = function (shortID) {
             var matches = Object.keys($scope.devices).filter(function (id) {
-                return id.substr(0, 7) === shortID;
+                return id.substr(0, shortIDStringLength) === shortID;
             });
             if (matches.length !== 1) {
                 return shortID;
@@ -1473,7 +1473,7 @@ angular.module('syncthing.core')
             if (match) {
                 return $scope.deviceName(match);
             }
-            return deviceID.substr(0, 6);
+            return deviceID.substr(0, shortIDStringLength);
         };
 
         $scope.deviceName = function (deviceCfg) {
@@ -1490,7 +1490,7 @@ angular.module('syncthing.core')
             if (typeof deviceID === 'undefined') {
                 return "";
             }
-            return deviceID.substr(0, 6);
+            return deviceID.substr(0, shortIDStringLength);
         };
 
         $scope.thisDeviceName = function () {
@@ -1501,7 +1501,7 @@ angular.module('syncthing.core')
             if (device.name) {
                 return device.name;
             }
-            return device.deviceID.substr(0, 6);
+            return device.deviceID.substr(0, shortIDStringLength);
         };
 
         $scope.showDeviceIdentification = function (deviceCfg) {