Merge pull request #105845 from lukegb/singleuser-fetchzip

fetchzip: get write permission on unpacked directory

pkgs/build-support/fetchzip/default.nix

@@ -48,8 +48,15 @@
     + extraPostFetch
     # Remove write permissions for files unpacked with write bits set
     # Fixes https://github.com/NixOS/nixpkgs/issues/38649
+    #
+    # However, we should (for the moment) retain write permission on the directory
+    # itself, to avoid tickling https://github.com/NixOS/nix/issues/4295 in
+    # single-user Nix installations. This is because in sandbox mode we'll try to
+    # move the path, and if we don't have write permissions on the directory,
+    # then we can't update the ".." entry.
     + ''
       chmod -R a-w "$out"
+      chmod u+w "$out"
     '';
 } // removeAttrs args [ "stripRoot" "extraPostFetch" ])).overrideAttrs (x: {
   # Hackety-hack: we actually need unzip hooks, too