ci: replace woodpecker with a forgejo actions workflow

Signed-off-by: Christoph Heiss <christoph@c8h4.io>

.forgejo/workflows/main.yaml

@@ -0,0 +1,38 @@
+---
+name: flake
+
+on:
+  push:
+
+env:
+  NIX_CONFIG: 'experimental-features = nix-command flakes'
+
+jobs:
+  build:
+    runs-on: nixos-unstable
+    steps:
+      - name: prepare nix container
+        run: |
+          nix-env -iA nixpkgs.nodejs nixpkgs.gnused nixpkgs.curl nixpkgs.gnupg
+
+      - name: checkout repository
+        uses: actions/checkout@v4
+
+      - name: prepare flake and secrets
+        run: |
+          set -x
+          for f in $(find secrets/ -type f -name '*.nix'); do
+            echo '{ }' > "$f";
+          done
+          # do not try to evaluate partly stubbed-out machine configs
+          regex='nixosConfigurations = \(.*\);$'
+          replacement='nixosConfigurations =\n          builtins.trace (\1) { };'
+          sed -i "s/$regex/$replacement/" flake.nix
+
+      - name: check git history
+        run: |
+          curl -L -o - 'https://c8h4.io/gpg.asc' | gpg --import
+          nix run .#check-git-history
+
+      - name: run flake check
+        run: nix flake check -L

.woodpecker.yml

@@ -1,43 +0,0 @@
----
-when:
-  - event: push
-
-clone:
-  - name: clone
-    image: woodpeckerci/plugin-git
-    settings:
-      depth: 0
-      partial: false
-
-steps:
-  - name: prepare
-    image: docker.io/nixos/nix
-    environment:
-      NIX_CONFIG: 'experimental-features = nix-command flakes'
-    commands:
-      - nix-env -iA nixpkgs.gnused
-      - for f in $(find secrets/ -type f -name '*.nix'); do echo '{ }' > "$f"; done
-      - >-
-        sed -i
-        's/nixosConfigurations = builtins.mapAttrs mkSystem machines;/nixosConfigurations =\n          builtins.trace (builtins.mapAttrs mkSystem machines) { };/'
-        flake.nix
-
-  - name: check-git-history
-    image: docker.io/nixos/nix
-    environment:
-      NIX_CONFIG: 'experimental-features = nix-command flakes'
-    depends_on:
-      - prepare
-    commands:
-      - nix-env -iA nixpkgs.curl nixpkgs.gnupg
-      - curl -L -o - 'https://c8h4.io/gpg.asc' | gpg --import
-      - nix run .#check-git-history
-
-  - name: flake-check
-    image: docker.io/nixos/nix
-    environment:
-      NIX_CONFIG: 'experimental-features = nix-command flakes'
-    depends_on:
-      - prepare
-    commands:
-      - nix flake check -L