Re: [PATCH 10/11] ref_transaction_verify(): new function to check a reference's value

>  /*
> - * Add a reference update to transaction.  new_sha1 is the value that
> - * the reference should have after the update, or null_sha1 if it should
> - * be deleted.  If old_sha1 is non-NULL, then it the value
> - * that the reference should have had before the update, or null_sha1 if
> - * it must not have existed beforehand.
> - * Function returns 0 on success and non-zero on failure. A failure to update
> - * means that the transaction as a whole has failed and will need to be
> - * rolled back.
> + * Add a reference update to transaction. new_sha1 is the value that
> + * the reference should have after the update, or null_sha1 if it
> + * should be deleted. If new_sha1 is NULL, then the reference is not
> + * changed at all. old_sha1 is the value that the reference must have
> + * before the update, or null_sha1 if it must not have existed
> + * beforehand. The old value is checked after the lock is taken to
> + * prevent races. If the old value doesn't agree with old_sha1, the
> + * whole transaction fails. If old_sha1 is NULL, then the previous
> + * value is not checked.
> + *
> + * Return 0 on success and non-zero on failure. Any failure in the
> + * transaction means that the transaction as a whole has failed and
> + * will need to be rolled back.