Commits on Nov 11, 2024

1. fix: better support dangling revisions …

   The submodules branch generates a checkout which depends on only the
   references, not all revisions. If there are dangling revisions in the
   bare fetcher clone (a correctness issue itself) then the subsequent
   temporary directory clone will disastrously fail with messages like
   ```
   fatal: reference is not a tree: 2da0785fa32ce4c628d501c8743c88be00835b50
   ```
   You should be able to reproduce this behavior with
   ```bash
   
   this_nixpkgs='github:nixos/nixpkgs?rev=36ac8d7e411eeb11ac0998d5a39e329c1226e541';
   this_git=$(nix build --print-out-paths "$this_nixpkgs#git")/bin/git;
   
   export GIT_AUTHOR_NAME=foo \
   	[email protected] \
   	GIT_AUTHOR_DATE=100000000 \
   	GIT_COMMITER_NAME=foo \
   	[email protected] \
   	GIT_COMMITTER_DATE=100000000;
   
   tmpgit=$(mktemp -d);
   echo "Repo'll be at $tmpgit";
   
   "$this_git" init "$tmpgit";
   
   "$this_git" -C "$tmpgit" commit --allow-empty -m "foo"; # 8c2146823865b76da067b3bb458611a0a19ede3b
   "$this_git" -C "$tmpgit" commit --allow-empty -m "foo"; # 2da0785fa32ce4c628d501c8743c88be00835b50
   "$this_git" -C "$tmpgit" reset --hard HEAD~1; # 8c2146823865b76da067b3bb458611a0a19ede3b
   
   for version in 18 19 20 21 22 23 24; do
       echo "Checking nix version 2.$version";
       this_nix=$(nix build "$this_nixpkgs#nixVersions.nix_2_$version^out" --print-out-paths)/bin/nix;
   
       url="file:///$tmpgit";
   
       # populate fetcher-v1.sqlite and the gitv3/ dir
       "$this_nix-build" --expr $'builtins.fetchGit {
           url = \"'"$url"$'\";
           rev = \"8c2146823865b76da067b3bb458611a0a19ede3b\";
           submodules = true;
       }';
   
       # put the "corrupted" git dir in place of the fetched one
       cache_dir="${XDG_CONFIG_HOME:-$HOME}"/.cache/nix/gitv3;
       tmp=$(mktemp);
       printf "%s" "$url" >"$tmp";
       fetched_dir="$cache_dir"/$(printf "%s" "$url" | $this_nix --extra-experimental-features nix-command hash file --type sha256 --base32 "$tmp");
       rm -rf "$fetched_dir";
       git clone --bare "$tmpgit" "$fetched_dir";
   
       # See if we can realise the derivation pointing to the dangling commit
       _NIX_FORCE_HTTP=1 "$this_nix-build" --impure --expr $'
       { pkgs ? (import <nixpkgs> { }) }: pkgs.stdenv.mkDerivation {
         pname = "foo";
         version = "1.0.0";
         dontUnpack = true;
   
         '"
         src = builtins.fetchGit {
           url = \"file:///$tmpgit\";
           rev = \"2da0785fa32ce4c628d501c8743c88be00835b50\";
           submodules = true;
         };
   
         buildPhase = ''
           touch \$out;
           exit 0;
         '';
       }
       "
   done
   ```
   This solution attempts to avoid the issue in the submodules path by
   simply checking out the specified revision (in addition to all
   references to preserve the original behavior - although, I think _only_
   the revision is necessary).

   

   johnrichardrinehart committed Nov 11, 2024
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