nixos/gitwatch: add module

Create module for gitwatch script. This module runs systemd services.
You are able to have several services for different paths at once.

Change-Id: If6100e883dd12a428f79881a80b9b88e683f6db9

nixos/modules/services/monitoring/gitwatch.nix

@@ -0,0 +1,87 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+let
+  mkSystemdService =
+    name: cfg:
+    lib.nameValuePair "gitwatch-${name}" (
+      let
+        getvar = flag: var: lib.optionalString (cfg."${var}" != null) "${flag} ${cfg."${var}"}";
+        branch = getvar "-b" "branch";
+        remote = getvar "-r" "remote";
+      in
+      rec {
+        inherit (cfg) enable;
+        after = [ "network-online.target" ];
+        wants = after;
+        wantedBy = [ "multi-user.target" ];
+        description = "gitwatch for ${name}";
+        path = with pkgs; [
+          gitwatch
+          git
+          openssh
+        ];
+        script = ''
+          if [ -n "${cfg.remote}" ] && ! [ -d "${cfg.path}" ]; then
+            git clone ${branch} "${cfg.remote}" "${cfg.path}"
+          fi
+          gitwatch ${remote} ${branch} ${cfg.path}
+        '';
+        serviceConfig.User = cfg.user;
+      }
+    );
+in
+{
+  options.services.gitwatch = lib.mkOption {
+    description = ''
+      A set of git repositories to watch for. See
+      [gitwatch](https://github.com/gitwatch/gitwatch) for more.
+    '';
+    default = { };
+    example = {
+      my-repo = {
+        enable = true;
+        user = "user";
+        path = "/home/user/watched-project";
+        remote = "git@github.com:me/my-project.git";
+      };
+      disabled-repo = {
+        enable = false;
+        user = "user";
+        path = "/home/user/disabled-project";
+        remote = "git@github.com:me/my-old-project.git";
+        branch = "autobranch";
+      };
+    };
+    type =
+      with lib.types;
+      attrsOf (submodule {
+        options = {
+          enable = lib.mkEnableOption "watching for repo";
+          path = lib.mkOption {
+            description = "The path to repo in local machine";
+            type = str;
+          };
+          user = lib.mkOption {
+            description = "The name of services's user";
+            type = str;
+            default = "root";
+          };
+          remote = lib.mkOption {
+            description = "Optional url of remote repository";
+            type = nullOr str;
+            default = null;
+          };
+          branch = lib.mkOption {
+            description = "Optional branch in remote repository";
+            type = nullOr str;
+            default = null;
+          };
+        };
+      });
+  };
+  config.systemd.services = lib.mapAttrs' mkSystemdService config.services.gitwatch;
+}