zfs_unstable: expand on unstable nature in long description

pkgs/os-specific/linux/zfs/generic.nix

@@ -26,6 +26,7 @@ let
   { version
   , hash
   , kernelModuleAttribute
+  , extraLongDescription ? ""
   , extraPatches ? []
   , rev ? "zfs-${version}"
   , kernelCompatible ? null
@@ -220,7 +221,7 @@ let
         snapshotting, cloning, block devices, deduplication, and more.
 
         ${if buildUser then "This is the userspace tools package." else "This is the kernel module package."}
-      '';
+      '' + extraLongDescription;
       homepage = "https://github.com/openzfs/zfs";
       changelog = "https://github.com/openzfs/zfs/releases/tag/zfs-${version}";
       license = lib.licenses.cddl;

pkgs/os-specific/linux/zfs/unstable.nix

@@ -28,4 +28,9 @@ callPackage ./generic.nix args {
   };
 
   hash = "sha256-/INlfiPpRm5JprcORzJJKyjpGIMY1LceY3yZ811uf2A=";
+
+  extraLongDescription = ''
+    This is "unstable" ZFS, and will usually be a pre-release version of ZFS.
+    It may be less well-tested and have critical bugs.
+  '';
 }