Add switch action to nixidy cli

modules/build.nix

@@ -55,6 +55,11 @@ in {
       internal = true;
       description = "The package containing all the applications for an environment.";
     };
+    build.activationPackage = mkOption {
+      type = types.package;
+      internal = true;
+      description = "The package containing all the applications and an activation script.";
+    };
   };
 
   config = {
@@ -90,5 +95,32 @@ in {
           config.build.extrasPackage
         ];
       };
+
+    build.activationPackage = pkgs.stdenv.mkDerivation {
+      name = "nixidy-activation-environment-${envName}";
+      phases = ["installPhase"];
+
+      installPhase = ''
+        mkdir -p $out
+
+        ln -s ${config.build.environmentPackage} $out/environment
+
+        cat <<EOF > $out/activate
+        #!/usr/bin/env bash
+        set -eo pipefail
+        dest="${config.nixidy.target.rootPath}"
+
+        mkdir -p "\$dest"
+
+        echo "switching manifests"
+
+        ${pkgs.rsync}/bin/rsync --recursive --delete -L "${config.build.environmentPackage}/" "\$dest"
+
+        echo "done!"
+        EOF
+
+        chmod +x $out/activate
+      '';
+    };
   };
 }

modules/default.nix

@@ -35,4 +35,5 @@ in {
     branch = module.config.nixidy.target.branch;
   };
   environmentPackage = module.config.build.environmentPackage;
+  activationPackage = module.config.build.activationPackage;
 }

nixidy/nixidy

@@ -50,6 +50,19 @@ function doBuild() {
   nix build "${FLAKE_ROOT}#nixidyEnvs.${NIX_SYSTEM}.${FLAKE_ENV}.environmentPackage" "${BUILD_PARAMS[@]}"
 }
 
+function doSwitch() {
+  setFlakeParam
+
+  if [[ -z "$FLAKE_ENV" ]]; then
+    doHelp
+    exit 1
+  fi
+
+  ENVIRON=$(nix build "${FLAKE_ROOT}#nixidyEnvs.${NIX_SYSTEM}.${FLAKE_ENV}.activationPackage" --no-link --print-out-paths)
+
+  "${ENVIRON}/activate"
+}
+
 function doHelp() {
     echo "Usage: $0 [OPTION] COMMAND"
     echo
@@ -70,6 +83,9 @@ function doHelp() {
     echo
     echo "  build FLAKE_URI  Build nixidy environment from flake URI."
     echo "                   Example: .#prod"
+    echo
+    echo "  switch FLAKE_URI Build and switch to nixidy environment from flake URI."
+    echo "                   Example: .#prod"
 }
 
 COMMAND=""
@@ -82,7 +98,7 @@ while [[ $# -gt 0 ]]; do
   opt="$1"
   shift
   case $opt in
-    build|info|help)
+    build|switch|info|help)
       COMMAND="$opt"
       ;;
     --no-link)
@@ -126,6 +142,9 @@ case $COMMAND in
   build)
     doBuild
     ;;
+  switch)
+    doSwitch
+    ;;
   help)
     doHelp
     ;;