docs: Update readme

README.md

@@ -1,8 +1,64 @@
 # Docker Slim
 
-A Docker image containing [Docker Slim](https://github.com/slimtoolkit/slim) for use with CI & CD pipelines
+**Status**: [![Create and publish a Docker image](https://github.com/liquidlight/docker-slim/actions/workflows/push-docker-image.yml/badge.svg)](https://github.com/liquidlight/docker-slim/actions/workflows/push-docker-image.yml)
 
-## Build Locally
+A Docker image containing [Docker Slim](https://github.com/slimtoolkit/slim) for use with CI & CD pipelines.
 
-- `docker build --build-arg="DOCKER_SLIM_VERSION=1.37.3" -t ghcr.io/liquidlight/docker-slim:1.37.3`
-- `slim build --target ghcr.io/liquidlight/docker-slim:1.37.3 --include-path /usr/local/bin/docker-slim --include-path /usr/local/bin/docker-slim-sensor --http-probe="false" --continue-after="1" --tag="ghcr.io/liquidlight/docker-slim:1.37.3-slim"`
+[Installing Docker Slim](https://github.com/slimtoolkit/slim#installation) is noted as a series of commands which xan be run as part of your pipeline. However, to save resources, time and a point of failure (if the machine at the time cannot execute the `curl` command) we thought it efficient to have it packaged ready to go.
+
+## Usage
+
+This image is designed to be used as the base image for a job within a CI/CD pipeline.
+
+We only have experience with Gitlab and Github, so PRs with examples for other tools would be appreciated.
+
+### Gitlab
+
+It is worth running `docker-slim` locally to ensure you get the parameters you need, some useful ones i've found:
+
+- `--http-probe="false"` combined with `--continue-after="1"` is handy if your docker image doesn't expose ports
+- `--include-path="/usr/local/bin/docker-slim"` - makes sure your custom scripts or files & folders are definitely included
+
+```yaml
+slim:image:build:
+  # Use the image with built-in docker slim
+  image: ghcr.io/liquidlight/docker-slim:1.37.3
+  # Specify input and output names
+  variables:
+    IMAGE_NAME: "$CI_REGISTRY_IMAGE:$CI_COMMIT_BRANCH"
+    SLIM_IMAGE_NAME: "$IMAGE_NAME-slim"
+  # Login to the registry
+  before_script:
+    # Login to our registry
+    - echo "$CI_REGISTRY_PASSWORD" | docker login $CI_REGISTRY --username $CI_REGISTRY_USER --password-stdin
+  script:
+    # Ensure that the fat image is cached locally
+    - docker pull $IMAGE_NAME
+    # Note regarding parameters: "--target" is the input, "--tag" is the output
+    - >
+      docker-slim build
+      --target="$IMAGE_NAME"
+      --tag="$SLIM_IMAGE_NAME"
+
+    # Push the slimmer image
+    - docker push $SLIM_IMAGE_NAME
+```
+
+## Github
+
+_Note:_ We haven't properly worked out how to use our image on Github Actions, so for now, the [Docker Slim GitHub Action](https://github.com/marketplace/actions/docker-slim-github-action) is available.
+
+There is an example [in this very repository](https://github.com/liquidlight/docker-slim/blob/main/.github/workflows/push-docker-image.yml).
+
+```yaml
+- name: Make a Slim image
+  uses: kitabisa/docker-slim-action@v1
+  env:
+    DSLIM_HTTP_PROBE: false
+  with:
+    target: ${{ env.IMAGE_NAME }}
+    tag: "${{ env.DOCKER_SLIM_VERSION }}-slim"
+
+  # Push to the registry
+  - run: docker push ${{ env.IMAGE_NAME }}-slim
+```