Do not add the release channel on stable versions of Atom

This is done to avoid changing the application user model id on Atom
stable, which prevents pins from currently installed Atom stable
versions to stop working.

src/main-process/start.js

@@ -73,10 +73,17 @@ module.exports = function start(resourcePath, devResourcePath, startTime) {
     return;
   }
 
-  // NB: This prevents Win10 from showing dupe items in the taskbar
-  app.setAppUserModelId(
-    'com.squirrel.atom.' + process.arch + getReleaseChannel(app.getVersion())
-  );
+  const releaseChannel = getReleaseChannel(app.getVersion());
+  let appUserModelId = 'com.squirrel.atom.' + process.arch;
+
+  // If the release channel is not stable, we append it to the app user model id.
+  // This allows having the different release channels as separate items in the taskbar.
+  if (releaseChannel !== 'stable') {
+    appUserModelId += `-${releaseChannel}`;
+  }
+
+  // NB: This prevents Win10 from showing dupe items in the taskbar.
+  app.setAppUserModelId(appUserModelId);
 
   function addPathToOpen(event, pathToOpen) {
     event.preventDefault();
@@ -93,7 +100,7 @@ module.exports = function start(resourcePath, devResourcePath, startTime) {
   app.on('will-finish-launching', () =>
     startCrashReporter({
       uploadToServer: config.get('core.telemetryConsent') === 'limited',
-      releaseChannel: getReleaseChannel(app.getVersion())
+      releaseChannel
     })
   );