fix: add Renovate custom managers for Dagger version in Dockerfile and DAGGER.md (#365)

Renovate only tracked the engine version in `ci/dagger.json`. This PR adds regex `customManagers` so Renovate also updates:
- `DAGGER_VERSION` in `.forgejo/Dockerfile`
- the nix flake reference (`github:dagger/nix/vX.Y.Z#dagger`) in `DAGGER.md`

All three now point to the same `dagger/dagger` GitHub releases datasource so they stay in sync via a single grouped PR.

Also bumps the stale `DAGGER.md` nix reference from `v0.11.4` to `v0.20.8` to match the current engine version.

Closes #358

Co-authored-by: Thomas SharedInbox <sharedinbox@thomas-guettler.de>
Reviewed-on: https://codeberg.org/guettli/sharedinbox/pulls/365

DAGGER.md

@@ -39,7 +39,7 @@ WorkingDirectory=/home/dagger-svc
 # Replace 1003 with the actual UID of dagger-svc
 Environment=DOCKER_HOST=unix:///run/user/1003/podman/podman.sock
 Environment=XDG_RUNTIME_DIR=/run/user/1003
-ExecStart=/usr/bin/nix run github:dagger/nix/v0.11.4#dagger -- engine --addr tcp://0.0.0.0:8080
+ExecStart=/usr/bin/nix run github:dagger/nix/v0.20.8#dagger -- engine --addr tcp://0.0.0.0:8080
 Restart=always
 
 [Install]

renovate.json

@@ -12,5 +12,23 @@
       "matchUpdateTypes": ["minor", "patch", "pin", "digest", "lockFileMaintenance"],
       "addLabels": ["automerge"]
     }
+  ],
+  "customManagers": [
+    {
+      "customType": "regex",
+      "fileMatch": ["^\\.forgejo/Dockerfile$"],
+      "matchStrings": ["DAGGER_VERSION=(?<currentValue>[0-9]+\\.[0-9]+\\.[0-9]+)"],
+      "depNameTemplate": "dagger/dagger",
+      "datasourceTemplate": "github-releases",
+      "extractVersionTemplate": "^v(?<version>.*)$"
+    },
+    {
+      "customType": "regex",
+      "fileMatch": ["^DAGGER\\.md$"],
+      "matchStrings": ["github:dagger/nix/v(?<currentValue>[0-9]+\\.[0-9]+\\.[0-9]+)#dagger"],
+      "depNameTemplate": "dagger/dagger",
+      "datasourceTemplate": "github-releases",
+      "extractVersionTemplate": "^v(?<version>.*)$"
+    }
   ]
 }