Make DOCKER_USERNAME and _PASSWORD optional

.github/workflows/test.yaml

@@ -39,5 +39,5 @@ jobs:
       uses: ./
       with:
         NO_PUSH: true
+        DOCKER_USERNAME: ${{ github.actor }}
         MYBINDERORG_TAG: ${{ github.sha }}
-

README.md

@@ -48,27 +48,22 @@ Images generated by this action are automatically tagged with both `latest` and
 
 See the [examples](#examples) section is very helpful for understanding the inputs and outputs of this Action.
 
-## Mandatory Inputs
-
-**Exception: if the input parameter `NO_PUSH` is set to any value, these values become optional.**
-
-- `DOCKER_USERNAME`:
-    description: Docker registry username
-- `DOCKER_PASSWORD`:
-    description: Docker registry password or [access token](https://docs.docker.com/docker-hub/access-tokens/).  **If using DockerHub, we recommend using an access token instead of your password.**
-
 ## Optional Inputs
 
+- **`DOCKER_USERNAME`**:
+    description: Docker registry username.  If not supplied, credentials must be setup ahead of time.
+- **`DOCKER_PASSWORD`**:
+    description: Docker registry password or [access token (recommended)](https://docs.docker.com/docker-hub/access-tokens/).  If not supplied, credentials must be setup ahead of time.
+- **`DOCKER_REGISTRY`**:
+    description: name of the docker registry.  If not supplied, this defaults to [DockerHub](https://hub.docker.com/)
+- **`IMAGE_NAME`**:
+    name of the image.  Example - myusername/myContainer.  If not supplied, this defaults to `<DOCKER_USERNAME/GITHUB_REPOSITORY_NAME>`.
 - **`NOTEBOOK_USER`**:
     description: username of the primary user in the image. If this is not specified, this is set to `joyvan`.  **NOTE**: This value is also overriden with `jovyan` if the parameters `BINDER_CACHE` or `MYBINDERORG_TAG` are provided.
 - **`REPO_DIR`**:
     Path inside the image where contents of the repositories are copied to, and where all the build operations (such as postBuild) happen. Defaults to `/home/<NOTEBOOK_USER>` if not set.
 - **`APPENDIX_FILE`**:
     Path to file containing Dockerfile commands to run at the end of the build. Can be used to customize the resulting image after all standard build steps finish.
-- **`IMAGE_NAME`**:
-    name of the image.  Example - myusername/myContainer.  If not supplied, this defaults to `<DOCKER_USERNAME/GITHUB_REPOSITORY_NAME>`.
-- **`DOCKER_REGISTRY`**:
-    description: name of the docker registry.  If not supplied, this defaults to [DockerHub](https://hub.docker.com/)
 - **`LATEST_TAG_OFF`**:
     Setting this variable to any value will prevent your image from being tagged with `latest`. Note that your image is always tagged with the [GitHub commit SHA](https://help.github.com/en/github/getting-started-with-github/github-glossary#commit).  
 - **`ADDITIONAL_TAG`**:
@@ -263,6 +258,8 @@ to any particular cloud vendor.
 
 ## Push Image To A Registry Other Than DockerHub
 
+If the docker registry accepts a credentials to be passed as a username and password string, you can do it like this.
+
 ```yaml
 name: Build Notebook Container
 on: [push]
@@ -282,6 +279,29 @@ jobs:
         DOCKER_REGISTRY: "gcr.io"
 ```
 
+If the docker registry doesn't credentials to be passed as a username and password strong, or if you want to do it in another way, you can configure credentials to the docker registry ahead of time instead.  Below is an incomplete example doing that.
+
+```yaml
+name: Build Notebook Container
+on: [push]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: checkout files in repo
+      uses: actions/checkout@main
+
+    # TODO: add a step here to setup credentials to push to your
+    #       docker registry before running the repo2docker-action
+
+    - name: update jupyter dependencies with repo2docker
+      uses: jupyterhub/repo2docker-action@master
+      with:
+        DOCKER_REGISTRY: your-registry
+        IMAGE_NAME: your-image-name
+```
+
 ## Change Image Name
 
 When you do not provide an image name your image name defaults to `DOCKER_USERNAME/GITHUB_REPOSITORY_NAME`.  For example if the user [`hamelsmu`](http://www.github.com/hamelsmu) tried to run this Action from this repo, it would be named `hamelsmu/repo2docker-action`.  However, sometimes you may want a different image name, you can accomplish by providing the `IMAGE_NAME` parameter as illustrated below:

action.yml

@@ -2,11 +2,11 @@ name: 'repo2docker Action'
 description: 'Creates a docker image of your repository to view the collection of notebooks'
 inputs:
   DOCKER_USERNAME:
-    description: Docker registry username
-    require: true
+    description: Docker registry username.  If not supplied, credentials must be setup ahead of time.
+    require: false
   DOCKER_PASSWORD:
-    description: Docker registry password
-    required: true
+    description: Docker registry password.  If not supplied, credentials must be setup ahead of time.
+    required: false
   DOCKER_REGISTRY:
     description: name of the docker registry.  If not supplied, this defaults to registry.hub.docker.com.
     require: false

create_docker_image.sh

@@ -18,22 +18,20 @@ if [ "$INPUT_APPENDIX_FILE" ]; then
     echo "Appendix read from $INPUT_APPENDIX_FILE:\n$APPENDIX"
 fi
 
-if [ -z "$INPUT_NO_PUSH" ]; then
-    check_env "INPUT_DOCKER_USERNAME"
-    check_env "INPUT_DOCKER_PASSWORD"
-    # Login to Docker registry
+# Login to Docker registry if about to push and credentials are passed
+if [[ -z "$INPUT_NO_PUSH" && -n "$INPUT_DOCKER_PASSWORD" && -n "$INPUT_DOCKER_USERNAME" ]]; then
     echo ${INPUT_DOCKER_PASSWORD} | docker login $INPUT_DOCKER_REGISTRY -u ${INPUT_DOCKER_USERNAME} --password-stdin
 fi
 
 REPO_NAME=`echo $GITHUB_REPOSITORY | cut -d "/" -f 2`
 
-# Set Docker username to the actor name not provided
-if [ -z "$INPUT_DOCKER_USERNAME" ]; then
-    INPUT_DOCKER_USERNAME="$GITHUB_ACTOR"
-fi
-
 # Set image name to username/repo_name if not provided
 if [ -z "$INPUT_IMAGE_NAME" ]; then
+    if [[ -z "$INPUT_DOCKER_USERNAME" ]]; then
+        echo "IMAGE_NAME must be explicitly set when DOCKER_USERNAME isn't set.  Exiting..."
+        exit 1
+    fi
+
     INPUT_IMAGE_NAME="$INPUT_DOCKER_USERNAME/$REPO_NAME"
     # Lower-case
     INPUT_IMAGE_NAME="${INPUT_IMAGE_NAME,,}"
@@ -45,7 +43,6 @@ if [ "$INPUT_DOCKER_REGISTRY" ]; then
 fi
 
 # Set username
-
 if [ -z "$INPUT_NOTEBOOK_USER" ] || [ "$INPUT_MYBINDERORG_TAG" ] || [ "$INPUT_BINDER_CACHE" ]; 
     then
         NB_USER="jovyan"
@@ -55,7 +52,6 @@ if [ -z "$INPUT_NOTEBOOK_USER" ] || [ "$INPUT_MYBINDERORG_TAG" ] || [ "$INPUT_BI
 fi
 
 # Set REPO_DIR
-
 if [ -z "$INPUT_REPO_DIR" ];
     then
         REPO_DIR="/home/${NB_USER}"