Restore more recent Android app tagged release

A prior change used the ironwood.1 tag to build the Android app in an
attempt to solve #289. Turns out that this change was unnecessary. So
here we revert to a more recent release of the Android app. Instead of
building from the master branch (which might create suprises) we build
from a fixed release tag.

The source repo and version are customisable via build arguments.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 Note: Breaking changes between versions are indicated by "💥".
 
+## Unreleased
+
+- [Improvement] Restore more recent Android app version (#289).
+
 ## v3.11.4 (2020-02-16)
 
 - [Bugfix] Fix auth problem in Android app (#289)

docs/extra.rst

@@ -43,7 +43,16 @@ With Tutor, you can build an Android mobile application for your platform. To bu
 
     tutor android build debug
 
-The ``.apk`` file will then be available in ``$TUTOR_ROOT/data/android``. Transfer it to an Android phone to install the application. You should be able to sign in and view available courses.
+The ``.apk`` file will then be available in ``$(tutor config printroot)/data/android``. Transfer it to an Android phone to install the application. You should be able to sign in and view available courses.
+
+Building a custom Android app
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The Android app is built from the `official edx-app-android repository <https://github.com/edx/edx-app-android/>`__. To change this repository or the app version, you can simply build a different docker image with::
+
+    tutor images build \
+        --build-arg ANDROID_APP_REPOSITORY=https://github.com/mycustomfork/edx-app-android \
+        --build-arg ANDROID_APP_VERSION=master
 
 Releasing an Android app
 ~~~~~~~~~~~~~~~~~~~~~~~~
@@ -56,7 +65,7 @@ Releasing an Android app on the Play Store requires to build the app in release
     ANDROID_RELEASE_KEY_PASSWORD
     ANDROID_RELEASE_KEY_ALIAS
 
-Then, place your keystore file in ``$TUTOR_ROOT/env/android/app.keystore``. Finally, build the application with::
+Then, place your keystore file in ``$(tutor config printroot)/env/android/app.keystore``. Finally, build the application with::
 
     tutor android build release
 

tutor/templates/build/android/Dockerfile

@@ -23,7 +23,9 @@ RUN wget https://dl.google.com/android/repository/sdk-tools-linux-${ANDROID_SDK_
 RUN yes | /openedx/android-sdk/tools/bin/sdkmanager "platforms;android-27" 1> /dev/null
 
 # Install android app repo
-RUN git clone https://github.com/edx/edx-app-android --branch open-release/ironwood.1 /openedx/edx-app-android
+ARG ANDROID_APP_REPOSITORY=https://github.com/edx/edx-app-android
+ARG ANDROID_APP_VERSION=release/2.20.2
+RUN git clone $ANDROID_APP_REPOSITORY --branch $ANDROID_APP_VERSION /openedx/edx-app-android
 WORKDIR /openedx/edx-app-android
 
 # Install gradle and all dependencies