Add murk and impermanence

modules/home/impermanence.nix

@@ -0,0 +1,50 @@
+{ pkgs, lib, config, osConfig, ... }:
+let
+  fs-diff = with pkgs;
+    writeShellApplication {
+      name = "fs-diff";
+      runtimeInputs = [ flameshot curl xsel ];
+      text = ''
+        #!/usr/bin/env bash
+        # fs-diff.sh
+        set -euo pipefail
+
+        OLD_TRANSID=$(sudo btrfs subvolume find-new /mnt/root-blank 9999999)
+        OLD_TRANSID=${OLD_TRANSID}
+
+        sudo mkdir /mnt
+        sudo mount -o subvol=/ /dev/mapper/crypted /mnt
+        sudo btrfs subvolume find-new "/mnt/root" "$OLD_TRANSID" |
+        sed \'$d\' |
+        cut -f17- -d' ' |
+        sort |
+        uniq |
+        while read path; do
+          path="/$path"
+          if [ -L "$path" ]; then
+            : # The path is a symbolic link, so is probably handled by NixOS already
+          elif [ -d "$path" ]; then
+            : # The path is a directory, ignore
+          else
+            echo "$path"
+          fi
+        done
+        sudo umount /mnt
+      '';
+    };
+in with lib; {
+  config = mkIf osConfig.mods.impermanence.enable {
+    home.packages = [ fs-diff ];
+    home.persistence."/persistent/home/muon" = {
+      directories = [
+        "documents"
+        "downloads"
+        "src"
+        ".gnupg"
+        ".ssh"
+        ".config/sops"
+        ".local/share/direnv"
+      ];
+    };
+  };
+}