environment.etc: Add convenience option 'text'

This allows writing

  environment.etc.hosts.text = "127.0.0.1 localhost";

instead of

  environment.etc.hosts.source = pkgs.writeText "hosts" "127.0.0.1 localhost";

modules/config/networking.nix

@@ -48,7 +48,7 @@ in
       "rpc".source = pkgs.glibc + "/etc/rpc";
 
       # /etc/hosts: Hostname-to-IP mappings.
-      "hosts".source = pkgs.writeText "hosts"
+      "hosts".text =
         ''
           127.0.0.1 localhost
           ${optionalString cfg.enableIPv6 ''
@@ -58,7 +58,7 @@ in
         '';
 
       # /etc/resolvconf.conf: Configuration for openresolv.
-      "resolvconf.conf".source = pkgs.writeText "resolvconf.conf" (
+      "resolvconf.conf".text =
           ''
             # This is the default, but we must set it here to prevent
             # a collision with an apparently unrelated environment
@@ -74,7 +74,7 @@ in
           '' + optionalString config.services.bind.enable ''
             # This hosts runs a full-blown DNS resolver.
             name_servers='127.0.0.1'
-          '' );
+          '';
     };
 
   # The ‘ip-up’ target is started when we have IP connectivity.  So

modules/system/etc/etc.nix

@@ -45,9 +45,6 @@ in
 
       options = singleton ({ name, config, ... }:
         { options = {
-            source = mkOption {
-              description = "Path of the source file.";
-            };
 
             target = mkOption {
               description = ''
@@ -57,6 +54,17 @@ in
               '';
             };
 
+            text = mkOption {
+              default = null;
+              type = types.nullOr types.string;
+              description = "Text of the file.";
+            };
+
+            source = mkOption {
+              types = types.path;
+              description = "Path of the source file.";
+            };
+
             mode = mkOption {
               default = "symlink";
               example = "0600";
@@ -71,6 +79,8 @@ in
 
           config = {
             target = mkDefault name;
+            source = mkIf (config.text != null)
+              (mkDefault (pkgs.writeText "etc-file" config.text));
           };
 
         });

modules/tasks/filesystems.nix

@@ -7,28 +7,6 @@ let
 
   fileSystems = attrValues config.fileSystems;
 
-  fstab = pkgs.writeText "fstab"
-    ''
-      # This is a generated file.  Do not edit!
-
-      # Filesystems.
-      ${flip concatMapStrings fileSystems (fs:
-          (if fs.device != null then fs.device else "/dev/disk/by-label/${fs.label}")
-          + " " + fs.mountPoint
-          + " " + fs.fsType
-          + " " + fs.options
-          + " 0"
-          + " " + (if fs.fsType == "none" || fs.device == "none" || fs.fsType == "btrfs" || fs.fsType == "tmpfs" || fs.noCheck then "0" else
-                   if fs.mountPoint == "/" then "1" else "2")
-          + "\n"
-      )}
-
-      # Swap devices.
-      ${flip concatMapStrings config.swapDevices (sw:
-          "${sw.device} none swap\n"
-      )}
-    '';
-
   fileSystemOpts = { name, ... }: {
 
     options = {
@@ -171,10 +149,27 @@ in
       [ pkgs.ntfs3g pkgs.cifs_utils ]
       ++ config.system.fsPackages;
 
-    environment.etc = singleton
+    environment.etc.fstab.text =
-      { source = fstab;
+      ''
-        target = "fstab";
+        # This is a generated file.  Do not edit!
-      };
+
+        # Filesystems.
+        ${flip concatMapStrings fileSystems (fs:
+            (if fs.device != null then fs.device else "/dev/disk/by-label/${fs.label}")
+            + " " + fs.mountPoint
+            + " " + fs.fsType
+            + " " + fs.options
+            + " 0"
+            + " " + (if fs.fsType == "none" || fs.device == "none" || fs.fsType == "btrfs" || fs.fsType == "tmpfs" || fs.noCheck then "0" else
+                     if fs.mountPoint == "/" then "1" else "2")
+            + "\n"
+        )}
+
+        # Swap devices.
+        ${flip concatMapStrings config.swapDevices (sw:
+            "${sw.device} none swap\n"
+        )}
+      '';
 
     # Provide a target that pulls in all filesystems.
     systemd.targets.fs =