feat: add custom nextcloud dockerfile and github action to publish docker image

Author: rizlas

README.md

@@ -1 +1,68 @@
-# nextcloud-docker
+# docker-nextcloud
+
+Custom Nextcloud Docker image that bakes the application code into the image,
+eliminating the rsync-on-startup pattern of the official image. Designed for Kubernetes
+deployments on NFS storage.
+
+## Key differences from the official image
+
+- **No `VOLUME /var/www/html`** — the application code lives in the image layer. Only
+  user-data directories (`config`, `data`, `custom_apps`, `themes`) are declared as
+  volumes.
+- **No rsync at startup** — code is copied at build time, not at runtime.
+- **Supports both Community and Enterprise** — select the edition via build args.
+- **Post-upgrade DB optimization** — runs `maintenance:repair`,
+  `db:add-missing-indices`, and related commands automatically after each upgrade
+  (opt-out via `NEXTCLOUD_SKIP_DATABASE_OPTIMIZATION=yes`).
+- **Subscription key support** — set `SUBSCRIPTION_KEY` to configure the enterprise
+  support app.
+
+## Build arguments
+
+|         Argument         |        Default        |                                     Description                                     |
+| ------------------------ | --------------------- | ----------------------------------------------------------------------------------- |
+| `NEXTCLOUD_VERSION`      | *(set in Dockerfile)* | Version to download (community)                                                     |
+| `ENTERPRISE_ARCHIVE_URL` | *(set in Dockerfile)* | If set, downloads the enterprise ZIP from this URL instead of the community tarball |
+
+## Volumes
+
+Only user-generated data needs to persist across image updates:
+
+|            Path             |                   Content                    |
+| --------------------------- | -------------------------------------------- |
+| `/var/www/html/config`      | Nextcloud configuration (`config.php`, etc.) |
+| `/var/www/html/data`        | User files                                   |
+| `/var/www/html/custom_apps` | User-installed apps                          |
+| `/var/www/html/themes`      | Custom themes                                |
+
+## Environment variables
+
+Additional variables introduced by this image:
+
+|                Variable                |  Default  |                        Description                         |
+| -------------------------------------- | --------- | ---------------------------------------------------------- |
+| `NEXTCLOUD_SKIP_DATABASE_OPTIMIZATION` | `no`      | Set to `yes` to skip post-upgrade DB optimization commands |
+| `SUBSCRIPTION_KEY`                     | *(unset)* | Enterprise subscription key for the `support` app          |
+
+## Upgrade behaviour
+
+The entrypoint detects the installed version from `config/version.php` (written after
+each successful install or upgrade) and compares it to the version baked in the image.
+
+- **Fresh install** (`config/version.php` absent): runs `occ maintenance:install`, then
+  writes the sentinel.
+- **Upgrade** (image version > installed version): runs `occ upgrade`, DB optimizations,
+  then updates the sentinel.
+- **Downgrade**: refused with an error.
+- **Cross-replica safety**: the init block is protected by `flock` on
+  `config/nextcloud-init-sync.lock` (on the shared `config` volume).
+
+## Files
+
+- `Dockerfile` — multi-stage build (`source` on alpine, `final` on
+  `php:8.4-apache-trixie`)
+- `docker-entrypoint.sh` — install/upgrade logic, structurally identical to the official
+  community entrypoint
+- `cron.sh` — runs `busybox crond` for background jobs
+- `config/` — default PHP config files baked into the image; also copied to
+  `/usr/src/nextcloud-config/` as a reference for drift detection warnings at startup