disko: add btrfs configuration for tungsten

nix/disko/tungsten/btrfs.nix

@@ -0,0 +1,92 @@
+{
+  disko.devices = {
+    disk = {
+      main = {
+        type = "disk";
+        device = "/dev/sda";
+        content = {
+          type = "gpt";
+          partitions = {
+            ESP = {
+              size = "500M";
+              type = "EF00";
+              content = {
+                type = "filesystem";
+                format = "vfat";
+                mountpoint = "/boot";
+                mountOptions = ["umask=0077"];
+              };
+            };
+
+            # Use LUKS for disk encryption
+            luks = {
+              size = "100%";
+              content = {
+                type = "luks";
+                name = "crypted";
+                extraOpenArgs = [];
+                settings.allowDiscards = true;
+                content = {
+                  type = "lvm_pv";
+                  vg = "pool";
+                };
+              };
+            };
+          };
+        };
+      };
+    };
+
+    # Use LVM to create a partition for swap
+    lvm_vg = {
+      pool = {
+        type = "lvm_vg";
+        lvs = {
+          # Set swap device as resume device
+          swap = {
+            size = "4G";
+            content = {
+              type = "swap";
+              discardPolicy = "both";
+              resumeDevice = true;
+            };
+          };
+
+          # Use btrfs over ext4 for:
+          # - compression
+          #   nix store can be shrinked using this feature
+          # - more transparent partitions (subvolumes)
+          #   no more "I need more space here and not there"
+          btrfs = {
+            size = "100%";
+            content = {
+              type = "btrfs";
+
+              mountpoint = "/btrfs-root";
+
+              # # DANGER:
+              # # Override existing partition at partition creation
+              # extraArgs = ["-f"];
+
+              subvolumes = {
+                "/root" = {
+                  mountpoint = "/";
+                };
+
+                "/home" = {
+                  mountOptions = ["compress=zstd"];
+                  mountpoint = "/home";
+                };
+
+                "/nix" = {
+                  mountOptions = ["compress=zstd" "noatime"];
+                  mountpoint = "/nix";
+                };
+              };
+            };
+          };
+        };
+      };
+    };
+  };
+}