[core] Stop handling beta, nightly

src/atom-environment.js

@@ -600,15 +600,15 @@ class AtomEnvironment {
   // Public: Gets the release channel of the Pulsar application.
   //
   // Returns the release channel as a {String}. Will return a specific release channel
-  // name like 'beta' or 'nightly' if one is found in the Pulsar version or 'stable'
+  // name like 'dev' if one is found in the Pulsar version or 'stable'
   // otherwise.
   getReleaseChannel() {
     return getReleaseChannel(this.getVersion());
   }
 
   // Public: Returns a {Boolean} that is `true` if the current version is an official release.
   isReleasedVersion() {
-    return this.getReleaseChannel().match(/stable|beta|nightly/) != null;
+    return this.getReleaseChannel().match(/stable|dev/) != null;
   }
 
   // Public: Get the time taken to completely load the current window.

src/command-installer.js

@@ -45,14 +45,12 @@ module.exports = class CommandInstaller {
   }
 
   getCommandNameForChannel(commandName) {
-    let channelMatch = this.appVersion.match(/beta|nightly/);
+    let channelMatch = this.appVersion.match(/dev/);
     let channel = channelMatch ? channelMatch[0] : '';
 
     switch (channel) {
-      case 'beta':
-        return `${commandName}-beta`;
-      case 'nightly':
-        return `${commandName}-nightly`;
+      case 'dev':
+        return `${commandName}-dev`;
       default:
         return commandName;
     }