Add a nix package

git-check-assertions.sh

@@ -41,6 +41,7 @@ for commit_hash in "${commits[@]}"; do
   echo "Checking out $commit_hash"
   git -c advice.detachedHead=false checkout -q "$commit_hash"
   commit_msg="$(git log -1 --format=%B "$commit_hash")"
+  # shellcheck disable=SC2016
   block="$(printf '%s\n' "$commit_msg" \
     | sed -n '/^```git-check-assertions[[:space:]]*$/,/^```[[:space:]]*$/p' \
     | sed '1d;$d')"