<nix/fetchurl.nix> ignores hashed mirrors for executables

[spacefrogg]

fetchurl.nix uses recursive hashing for executables. (I guess, that enables (re-)storing access bits.) The fetcher code explicitly excludes store paths with recursive hashes. (I guess again, because hashed-mirrors do not support directories.)

The bug/protocol deficiency is that nix cannot distinguish between the two. It looks like, it only concerns the busybox binary that builds the stdenv and it is only relevant when using hashed-mirrors (i.e. in an enterprise-environment without access to a substituter).

Question
Is it really necessary to store executable files as executables on the server? Would it not be easier to make files, marked executable, executable after download?

I'd be happy to supply a fix but want to check first if there is any interest in fixing this in the first place.

Current Workaround
It is not a show stopper for the sketched scenario but bad enough. The current workaround for nixpkgs is to do something along the lines of:

import nixpkgs { stdenvStages = args: 
  import (nixpkgs + /pkgs/stdenv/linux) (args // {
    bootstrapFiles = import ./files-with-fixed-urls.nix; 
  });
}

[stale]

I marked this as stale due to inactivity. → More info