[GH] Move playground projects into a separate folder

This PR updates the GitHub setup to position playground projects outside the main project structure.

This is done for 2 reasons:

* Running `gw` (gradle shortcut that finds the closest gradlew) would match the playground gradlew even when the developer is not using playground
* Android studio would pick the playground settings.gradle file when running jvm tests from studio's gutter icon. This caused a lot of confusion for developers as it might run with different dependencies, confuse studio etc.

This updates moves them into playground-projects folder, also names each one as `projectName-playground` to further avoid any confusion with the parent project (e.g. :room gets included automatically when :room-common is included, we don't want it to conflict with the playground root project).

I updated the workflow files to use the new setup (PR will fail on target since it will use the old workflow file)
I've also added an empty playground project to run ktlint on CI so that it doesn't get affected by other projects.

Bug: n/a
Test: CI

This is an imported pull request from #624.

Resolves #624
Github-Pr-Head-Sha: ebfcbba
GitOrigin-RevId: c1db28e
Change-Id: I6c2176678187dc5f043cdb4391496ee372834c7f

.github/workflows/presubmit.yml

@@ -99,14 +99,14 @@ jobs:
 
           # Limit the size of the cache entry.
           # These directories contain instrumented/transformed dependency jars which can be reconstructed relatively quickly.
-          gradle-home-cache-excludes: | 
+          gradle-home-cache-excludes: |
             caches/jars-9
             caches/transforms-3
 
       - name: "ktlint"
         env:
           JAVA_HOME: ${{ steps.setup-java.outputs.path }}
-        working-directory: activity
+        working-directory: playground-projects/ktlint-playground
         run: ./gradlew -q :ktlintCheckFile ${{ steps.ktlint-file-args.outputs.ktlint-file-args }} ${{ needs.setup.outputs.gradlew_flags }}
 
   build-modules:
@@ -126,7 +126,7 @@ jobs:
     needs: [setup, lint]
     env:
       artifact-id: ${{matrix.project}}
-      project-root: ${{matrix.project-root || matrix.project}}
+      project-root: playground-projects/${{matrix.project-root || matrix.project}}-playground
       GRADLE_BUILD_CACHE_PASSWORD: ${{ secrets.GRADLE_BUILD_CACHE_PASSWORD }}
       GRADLE_ENTERPRISE_ACCESS_KEY: ${{ secrets.GRADLE_ENTERPRISE_ACCESS_KEY }}
     steps:
@@ -145,7 +145,7 @@ jobs:
         if: ${{ steps.check-ci-config.outputs.enabled == 'true' }}
         with:
           project: ${{ matrix.project }}
-          project-root: ${{matrix.project-root || matrix.project }}
+          project-root: ${{ env.project-root }}
           gradle-cache-password: ${{ secrets.GRADLE_BUILD_CACHE_PASSWORD }}
           gradle-enterprise-access-key: ${{ secrets.GRADLE_ENTERPRISE_ACCESS_KEY }}
           gradle-flags: ${{ needs.setup.outputs.gradlew_flags }}

CONTRIBUTING.md

@@ -39,7 +39,7 @@ creating a fork of the [androidx/androidx](https://github.com/androidx/androidx)
 
 - Download and install JDK 17, if you don’t have it already.
 
-  Note the installation directory. If you already have JDK 17 installed and set as default, you can 
+  Note the installation directory. If you already have JDK 17 installed and set as default, you can
   find this with `which javac`.
 
 - Download and install [Android Studio](https://developer.android.com/studio) if you don't have it
@@ -85,6 +85,9 @@ androidx
   -- work
 ```
 
+To avoid conflict with the main project, these sub project groups are located under the
+`playground-projects` folder.
+
 **Note:** For other projects, you will still need to use the Gerrit workflow used by the Android Open Source Project (AOSP). For more information, please look at the [README](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:README.md).
 
 Fork the [androidx/androidx](https://github.com/androidx/androidx) repository.
@@ -109,7 +112,7 @@ Let’s assume that you want to make a contribution to Room. The first step is t
 First launch Android Studio using:
 
 ```bash
-cd androidx/room
+cd playground-projects/room-playground
 # This will automatically launch the `room` project in Android Studio.
 ./gradlew studio
 ```