Function prepare_single_update

refs/reftable-backend.c:1042–1291

}

static enum ref_transaction_error prepare_single_update(struct reftable_ref_store *refs,
							struct reftable_transaction_data *tx_data,
							struct ref_transaction *transaction,
							struct reftable_backend *be,
							struct ref_update *u,
							size_t update_idx,
							struct string_list *refnames_to_check,
							unsigned int head_type,
							struct strbuf *head_referent,
							struct strbuf *referent,
							struct strbuf *err)
{
	enum ref_transaction_error ret = 0;
	struct object_id current_oid = {0};
	const char *rewritten_ref;

	/*
	 * There is no need to reload the respective backends here as
	 * we have already reloaded them when preparing the transaction
	 * update. And given that the stacks have been locked there
	 * shouldn't have been any concurrent modifications of the
	 * stack.
	 */
	ret = backend_for(&be, refs, u->refname, &rewritten_ref, 0);
	if (ret)
		return REF_TRANSACTION_ERROR_GENERIC;

	if (u->flags & REF_LOG_USE_PROVIDED_OIDS) {
		if (!(u->flags & REF_HAVE_OLD) ||
		    !(u->flags & REF_HAVE_NEW) ||
		    !(u->flags & REF_LOG_ONLY)) {
			strbuf_addf(err, _("trying to write reflog for '%s' "
					   "with incomplete values"), u->refname);
			return REF_TRANSACTION_ERROR_GENERIC;
		}

		if (queue_transaction_update(refs, tx_data, u, &u->old_oid, err))
			return REF_TRANSACTION_ERROR_GENERIC;
		return 0;
	}

	/*
	 * When we update the reference that HEAD points to we enqueue
	 * a second log-only update for HEAD so that its reflog is
	 * updated accordingly.
	 */
	if (head_type == REF_ISSYMREF &&
	    !(u->flags & REF_LOG_ONLY) &&
	    !(u->flags & REF_UPDATE_VIA_HEAD) &&
	    !strcmp(rewritten_ref, head_referent->buf)) {
		/*
		 * First make sure that HEAD is not already in the
		 * transaction. This check is O(lg N) in the transaction
		 * size, but it happens at most once per transaction.
		 */
		if (string_list_has_string(&transaction->refnames, "HEAD")) {
			/* An entry already existed */
			strbuf_addf(err,