egit

//-----------------------------------------------------------------------------
// libgit2 "cherry-pick" - apply a single commit to current branch
//-----------------------------------------------------------------------------
#pragma once

#include <git2/cherrypick.h>

ERL_NIF_TERM lg2_cherry_pick(ErlNifEnv* env, git_repository* repo, std::string const& commit_oid_str)
{
  git_oid commit_oid;
  if (git_oid_fromstr(&commit_oid, commit_oid_str.c_str()) != GIT_OK)
    return make_git_error(env, std::format("Invalid commit OID: {}", commit_oid_str));

  SmartPtr<git_commit> commit(git_commit_free);
  if (git_commit_lookup(&commit, repo, &commit_oid) != GIT_OK)
    return make_git_error(env, std::format("Failed to lookup commit {}", commit_oid_str));

  git_cherrypick_options options = GIT_CHERRYPICK_OPTIONS_INIT;

  int result = git_cherrypick(repo, commit, &options);

  if (result == GIT_OK) {
    return ATOM_OK;
  } else if (result == GIT_EMERGECONFLICT) {
    SmartPtr<git_index> index(git_index_free);
    if (git_repository_index(&index, repo) == GIT_OK) {
      std::vector<ERL_NIF_TERM> conflicts;

      for (size_t i = 0; i < git_index_entrycount(index); ++i) {
        auto entry = git_index_get_byindex(index, i);
        if (entry) {
          unsigned int stage = GIT_INDEX_ENTRY_STAGE(entry);
          if (stage != 0) {
            conflicts.push_back(make_binary(env, std::string_view(entry->path)));
          }
        }
      }

      if (!conflicts.empty()) {
        auto conflict_list = make_list(env, conflicts);
        return enif_make_tuple2(env, ATOM_CONFLICT, conflict_list);
      }
    }
    return make_git_error(env, "Cherry-pick conflict occurred");
  } else {
    return make_git_error(env, "Failed to cherry-pick commit");
  }
}