Add a script for updating the Hackage rev

Author: rvl

default.nix

@@ -84,6 +84,11 @@ let
     # Snapshots of Hackage and Stackage, converted to Nix expressions,
     # regularly updated.
     inherit hackage stackage;
+
+    # Scripts for keeping Hackage and Stackage up to date.
+    maintainer-scripts = {
+      update-hackage = self.callPackage ./scripts/update-hackage.nix {};
+    };
   });
 
 in

scripts/update-hackage.nix

@@ -0,0 +1,36 @@
+{ stdenv, writeScriptBin, coreutils, git, nix-tools, cabal-install, nix-prefetch-git }:
+
+with stdenv.lib;
+
+writeScriptBin "update-hackage-nix" ''
+  #!${stdenv.shell}
+
+  set -euo pipefail
+
+  export PATH="${makeBinPath [ coreutils git nix-tools cabal-install nix-prefetch-git ]}"
+
+  # Make sure the hackage index is recent.
+  cabal new-update
+
+  if [ -d hackage.nix ]; then
+    cd hackage.nix
+    git pull --ff-only
+    cd ..
+  else
+    git clone [email protected]:input-output-hk/hackage.nix.git
+  fi
+
+  hackage-to-nix hackage.nix
+
+  cd hackage.nix
+  git add .
+  git commit --allow-empty -m "Automatic update for $(date)"
+
+  rev=$(git rev-parse HEAD)
+
+  git push
+
+  cd ..
+
+  nix-prefetch-git https://github.com/input-output-hk/hackage.nix.git --rev "$rev" | tee hackage-src.json
+''