Combine the build and test workflows into single file

.github/workflows/build.yaml

@@ -4,6 +4,9 @@ on:
   push:
     branches:
       - main
+  pull_request:
+    branches:
+      - main
 
 jobs:
   build-and-push:
@@ -23,9 +26,11 @@ jobs:
     - name: Checkout files in repo
       uses: actions/checkout@main
 
-    - name: Build and push the image to quay.io
+    - name: Build the image and push to quay.io if not a pull request
       uses: jupyterhub/repo2docker-action@master
       with:
+        # Don't push the image during a PR build
+        NO_PUSH: "${{ github.event_name == 'pull_request' }}"
         # Make sure username & password/token pair matches your registry credentials
         DOCKER_USERNAME: ${{ secrets.QUAY_USERNAME }}
         DOCKER_PASSWORD: ${{ secrets.QUAY_PASSWORD }}

README.md

@@ -34,22 +34,20 @@ The `repo2docker-action` will update the [base repo2docker](https://github.com/j
 **Note:**
 A complete list of possible configuration files that can be added to the repository and be used by repo2docker to build the Docker image, can be found in the [repo2docker docs](https://repo2docker.readthedocs.io/en/latest/config_files.html#configuration-files).
 
-### The GitHub workflows
+### The GitHub Action workflows
 
-This template repository provides two GitHub workflows that can build and push the image to quay.io when configured.
+This template repository provides some GitHub Action workflows that can build and push the image to quay.io when configured, and test the image on Binder.
 
 ![Workflows](images/workflows.png)
 
 #### 1. Build and push container image :arrow_right: [build.yaml](https://github.com/2i2c-org/hub-user-image-template/blob/main/.github/workflows/build.yaml)
 
-This workflow is triggered by every pushed commit on the main branch of the repo (including when a PR is merged).
-It **builds** the image and **pushes** it to the registry.
+This workflow is triggered by every pushed commit on the main branch of the repo (including when a PR is merged), and every commit made to a Pull Request opened against the default branch (`main`)..
+It **builds** the image and **pushes** it to the registry _on pushes to the default branch_.
+During PR builds, the image is **only** built and **not** pushed, unless explicitly configured to do so.
+Checkout [this section](https://docs.2i2c.org/en/latest/admin/howto/environment/hub-user-image-template-guide.html#enable-quay-io-image-push-during-pull-requests) on how to enable image pushes on Pull Requests.
 
-#### 2. Test container image build :arrow_right: [test.yaml](https://github.com/2i2c-org/hub-user-image-template/blob/MAIN/.github/workflows/test.yaml)
-
-This workflow is triggerd by every Pull Request commit and it **builds** the image, but it **doesn't** push it to the registry, unless explicitly configured to do so. Checkout [this section](https://docs.2i2c.org/en/latest/admin/howto/environment/hub-user-image-template-guide.html#enable-quay-io-image-push-for-test-yaml) on how to enable image pushes on Pull Requests.
-
-#### 3. Test this PR on Binder Badge :arrow_right: [binder.yaml](https://github.com/2i2c-org/hub-user-image-template/blob/MAIN/.github/workflows/binder.yaml)
+#### 2. Test this PR on Binder Badge :arrow_right: [binder.yaml](https://github.com/2i2c-org/hub-user-image-template/blob/MAIN/.github/workflows/binder.yaml)
 
 This workflow posts a comment inside a pull request, every time a pull request gets opened. The comment contains a "Test this PR on Binder" badge, which can be used to access the image defined by the PR in [mybinder.org](https://mybinder.org/).