all-cabal-hashes: Set name

Used to be just the hash from the basename, which was
not informative when appearing in logs etc.

pkgs/data/misc/hackage/default.nix

@@ -1,10 +1,11 @@
 # Hackage database snapshot, used by maintainers/scripts/regenerate-hackage-packages.sh
 # and callHackage
-{ fetchurl }:
+{ lib, fetchurl }:
 let
   pin = builtins.fromJSON (builtins.readFile ./pin.json);
 in
 fetchurl {
   inherit (pin) url sha256;
+  name = "all-cabal-hashes-${lib.substring 0 7 pin.commit}.tar.gz";
   passthru.updateScript = ../../../../maintainers/scripts/haskell/update-hackage.sh;
 }