add flag support

example/config-gpt-bios.nix

@@ -0,0 +1,33 @@
+# Example to create a bios compatible gpt partition
+{
+  type = "devices";
+  content = {
+    sda = {
+      type = "table";
+      format = "gpt";
+      partitions = [
+        {
+          type = "partition";
+          start = "0";
+          end = "1M";
+          part-type = "primary";
+          flags = ["bios_grub"];
+          content.type = "noop";
+        }
+        {
+          type = "partition";
+          # leave space for the grub aka BIOS boot
+          start = "1M";
+          end = "100%";
+          part-type = "primary";
+          bootable = true;
+          content = {
+            type = "filesystem";
+            format = "ext4";
+            mountpoint = "/";
+          };
+        }
+      ];
+    };
+  };
+}

example/config.nix

@@ -24,6 +24,7 @@
           part-type = "primary";
           start = "1024MiB";
           end = "100%";
+          flags = [ "bios_grub" ];
           content = {
             type = "luks";
             algo = "aes-xts...";

example/default.nix

@@ -3,11 +3,13 @@
 let
   # TODO: get rid of NIX_PATH dependency here
   pkgs = import <nixpkgs> {};
+  cfg = import ./config.nix;
+  #cfg = import ./config-gpt-bios.nix;
 in
 with import ../lib { inherit (pkgs) lib;};
 
 {
-  config = config (import ./config.nix);
-  create = create (import ./config.nix);
-  mount = mount (import ./config.nix);
+  config = config cfg;
+  create = create cfg;
+  mount = mount cfg;
 }

lib/default.nix

@@ -75,6 +75,9 @@ let {
     ${optionalString (x.bootable or false) ''
       parted -s ${q.device} set ${toString q.index} boot on
     ''}
+    ${concatMapStringsSep "" (flag: ''
+      parted -s ${q.device} set ${toString q.index} ${flag} on
+    '') (x.flags or [])}
     ${create-f { device = q.device + toString q.index; } x.content}
   '';