ci: add docker image build

.gitea/workflows/docker.yaml

@@ -0,0 +1,12 @@
+name: Build a docker image.
+on: [push]
+
+jobs:
+  build-docker-image:
+    runs-on: nixos
+    steps:
+      - name: Check out repository code
+        uses: actions/checkout@v4
+
+      - name: Build flake
+        run: nix build .#docker

flake.nix

@@ -13,6 +13,12 @@
         overlays.avcpp = final: prev: {
           avcpp = final.callPackage ./nix/avcpp.nix {};
         };
+        overlays.lib = final: prev: {
+          lib = prev.lib.extend (_: _:
+            import ./nix/lib.nix {
+              inherit (final) lib;
+            });
+        };
       };
       systems = [
         "x86_64-linux"
@@ -28,12 +34,14 @@
           overlays = [
             self.overlays.mosh-me
             self.overlays.avcpp
+            self.overlays.lib
           ];
           config = {};
         };
 
         packages.default = pkgs.mosh-me;
         packages.mosh-me = pkgs.mosh-me;
+        packages.docker = pkgs.callPackage ./nix/docker.nix {tag = pkgs.lib.gitRevOrLastModified self;};
 
         devShells.default = self'.devShells.mosh-me;
         devShells.mosh-me = pkgs.mkShell {

nix/docker.nix

@@ -0,0 +1,27 @@
+{
+  buildEnv,
+  dockerTools,
+  runtimeShell,
+  tag ? "latest",
+  mosh-me,
+  ...
+}:
+dockerTools.buildImage {
+  name = "mosh-me";
+  inherit tag;
+  created = "now";
+  copyToRoot = buildEnv {
+    name = "image-root";
+    paths = [mosh-me];
+    pathsToLink = ["/bin"];
+  };
+  runAsRoot = ''
+    #!${runtimeShell}
+    mkdir -p /pwd
+  '';
+
+  config = {
+    Cmd = ["/bin/mosh-me"];
+    WorkingDir = "/pwd";
+  };
+}

nix/lib.nix

@@ -0,0 +1,9 @@
+{lib, ...}: let
+  firstNonNull = xs: lib.findFirst (x: x != null) "unknown" xs;
+in {
+  gitRevOrLastModified = flake:
+    firstNonNull [
+      (lib.mapNullable (r: "git-" + r) (flake.shortRev or flake.rev or null))
+      (lib.mapNullable (n: "from-" + (lib.toLower n)) flake.sourceInfo.lastModifiedDate or null)
+    ];
+}