New project dialog's "Install SDK" button installs Flutter with the alpha channel

[gazialankus]

Steps to Reproduce

1. Install IntelliJ and Flutter plugin without installing the Flutter SDK.
2. Start creating a new Flutter project.
3. Click on the Install SDK button on the top right, right under the Flutter SDK path text box.
4. Verify this via Tools->Flutter->Flutter doctor

Also, you're stuck at alpha:
5. Try Tools->Flutter->Flutter Upgrade. It tries to switch from alpha to dev without success.
6. Go to command line and try flutter channel dev. Try flutter channel again and see that you're still in alpha.
7. Do flutter channel master followed by flutter channel dev to go to dev channel.

I guess I found the line with the issue:

flutter-intellij/src/io/flutter/module/InstallSdkAction.java

Line 332 in 72db65a

.withParameters("clone", "-b", "alpha", "https://github.com/flutter/flutter.git");

The above code clones the alpha branch, while the instructions tell us to clone the dev branch: https://flutter.io/setup-windows/#clone-the-repo

Version info

λ flutter doctor -v
[√] Flutter (Channel master, v0.1.6-pre.7, on Microsoft Windows [Version 10.0.16299.192], locale en-US)
• Flutter version 0.1.6-pre.7 at C:\Installs\Flutter\flutter
• Framework revision c3bbcb6f91 (24 hours ago), 2018-02-24 09:28:58 -0800
• Engine revision ead227f118
• Dart version 2.0.0-dev.28.0.flutter-0b4f01f759

[√] Android toolchain - develop for Android devices (Android SDK 27.0.3)
• Android SDK at D:\Installs\Android\sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-27, build-tools 27.0.3
• ANDROID_HOME = D:\Installs\Android\sdk
• Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b01)

[√] Android Studio (version 3.0)
• Android Studio at C:\Program Files\Android\Android Studio
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b01)

[√] IntelliJ IDEA Ultimate Edition (version 2017.3)
• Flutter plugin version 22.0.2
• Dart plugin version 173.4548.30

[!] VS Code (version 1.17.2)
• VS Code at C:\Program Files\Microsoft VS Code
• Dart Code extension not installed; install from
https://marketplace.visualstudio.com/items?itemName=Dart-Code.dart-code

[!] Connected devices
! No devices available

! Doctor found issues in 2 categories.