add workflow and documentation for OCI release

.github/workflows/release-chart.yaml

@@ -0,0 +1,30 @@
+# Publish chart as OCI image to GitHub registry. Version is automatically gathered from the tag name.
+# For this workflow to work, GITHUB_TOKEN needs to be configured with write permissions.
+# Additionally, the repository must be granted access in the package settings.
+
+name: Publish chart
+
+on:
+  release:
+    types: [ released ]
+
+jobs:
+  release:
+    name: Publish chart to OCI registry
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Helm login
+        run: |
+          echo "${{ secrets.GITHUB_TOKEN }}" | \
+          helm registry login ghcr.io \
+            --username "$GITHUB_REPOSITORY_OWNER" \
+            --password-stdin
+      - name: Helm package
+        run: |
+          helm package . -u --version "${GITHUB_REF_NAME#v}"
+      - name: Helm push
+        run: |
+          helm push \
+          "mastodon-${GITHUB_REF_NAME#v}.tgz" \
+          "oci://ghcr.io/$GITHUB_REPOSITORY_OWNER/charts"

Chart.yaml

@@ -12,10 +12,10 @@ description: Mastodon is a free, open-source social network server based on Acti
 # pipeline. Library charts do not define any templates and therefore cannot be deployed.
 type: application
 
-# This is the chart version. This version number should be incremented each time
-# you make changes to the chart and its templates, including the app version.
-# Versions are expected to follow Semantic Versioning (https://semver.org/)
-version: 5.1.1
+# Chart version is set to 0.0.0 in the source tree. The release pipeline replaces this with the version
+# being released in build time.
+# Please refer to git tags and/or GitHub releases to check out the latest version.
+version: 0.0.0
 
 # This is the version number of the application being deployed. This version number should be
 # incremented each time you make changes to the application. Versions are not expected to

README.md

@@ -17,6 +17,23 @@ We still encourage suggestions and PRs to help make this chart better, and this
 
 Please see the pinned [GitHub issue](https://github.com/mastodon/chart/issues/129) for more info & discussion.
 
+# Installation
+
+This chart is [released as an OCI image](https://helm.sh/docs/topics/registries/) to `ghcr.io/mastodon/charts/mastodon`. You can install it without the need to add any repository to your helm installation using:
+
+```shell
+helm install mastodon oci://ghcr.io/mastodon/charts/mastodon --values your-values-file.yaml
+```
+
+You can also add it as a dependency to another chart in your Chart.yaml:
+
+```yaml
+dependencies:
+  - name: mastodon
+    version: 4.0.0
+    repository: oci://ghcr.io/mastodon/charts
+```
+
 # Configuration
 
 The variables that _must_ be configured are: