Problem with fetchpatch #nix #patch #nixpkgs

readme.md

Patches are only applied if the have the right format. In other words a simple git diff to generate them does not work. Using git commit -a (temporary commit i. e. named "changes"), then git format-patch (for that to work you need to have username and email set in git config), followed by git reset --[hard|mixed] <SHA of last not temporary commit> should work. Test using git am < 0001-changes.patch before uploading 0001-changes.patch elsewhere. Now the more probelmatic issue: If you set to patch i. e. nixpkgs using the approach here NixOS/nixpkgs#111651 (comment) you first need to give it a (wrong) sha to provoke getting the right one, i. e. use nix-hash --flat --type sha256 0001-changes.patch and put the output in fetchpatches sha256 field. The build will then output an error saying "got: sha256:". That one you can finally put in the sha256 field and then the build should output i. e. "applying patch /nix/store/8q1lhja5kbmnmynsqxzwf4pqfkpjsssm-nixpkgs-0001-changes.patch (...) patching file".

NOPE

It's just the derivation was built and in nix-store already. So to have the patches (re-)applied you need to delete the according nix-store entries or change the derivation name.

Mic92/nixos-shell#26

default.nix

let
  nixpkgsPatches = [
      {
         name = "nixpkgs-qemu-5.2.0-desktop.patch";
         sha256 = "sha256:0255mav4sc556dzmapmyfz2x3a92ch6hhmyp60vycj47fvs6gf91";
         url = "https://gist.githubusercontent.com/573/29b1ad750bd88102177e8dcdfcaf540e/raw/6b65e4a9102f5490388a7f096903b1129d85c6a9/qemu-5.2.0-111651.patch";
      }
];
  localNixpkgsPatches = [
  ];

  patches = map hostPkgs.fetchpatch nixpkgsPatches ++ localNixpkgsPatches;

  hostPkgs = import <nixpkgs> {};
  patchedPkgs = hostPkgs.runCommand "nixpkgs-patched-11" { inherit patches; pkgs = hostPkgs.path; } ''
    cp -r $pkgs $out
    chmod -R +w $out
    for p in $patches; do
      echo "Applying patch $p";
      patch -d $out -N -p1 < "$p";
    done
  '';
  pkgs = import patchedPkgs {}; 
in
# https://archive.vn/wip/XEeuK (hostPkgs)
with import patchedPkgs {};
stdenv.mkDerivation {
  name = "nixos-shell";
  src = ./.;
  buildInputs = [ bash ];
  preConfigure = ''
    export PREFIX=$out
  '';
}