Re: [PATCH 11/16] refs: move duplicate check to common code

> The check for duplicate refnames in a transaction is needed for
> all backends, so move it to the common code.
> 
> ref_transaction_commit_fn gains a new argument, the sorted
> string_list of affected refnames.
> 
> Signed-off-by: David Turner <dturner@twopensource.com>
> ---
>  refs.c               | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++--
>  refs/files-backend.c | 57 ++++-------------------------------------
>  refs/refs-internal.h |  1 +
>  3 files changed, 75 insertions(+), 54 deletions(-)
> 
> diff --git a/refs.c b/refs.c
> index 1b79630..808053f 100644
> --- a/refs.c
> +++ b/refs.c
> @@ -1093,6 +1093,37 @@ const char *find_descendant_ref(const char *dirname,
>  	return NULL;
>  }
>  
> +/*
> + * Return 1 if there are any duplicate refnames in the updates in
> + * `transaction`, and fill in err with an appropriate error message.
> + * Fill in `refnames` with the refnames from the transaction.
> + */
> +
> +static int ref_update_reject_duplicates(struct ref_transaction *transaction,
> +					struct string_list *refnames,
> +					struct strbuf *err)

> +{
> +	int i, n = transaction->nr;
> +	struct ref_update **updates;
> +
> +	assert(err);
> +
> +	updates = transaction->updates;
> +	/* Fail if a refname appears more than once in the transaction: */
> +	for (i = 0; i < n; i++)
> +		string_list_append(refnames, updates[i]->refname);
> +	string_list_sort(refnames);
> +
> +	for (i = 1; i < n; i++)
> +		if (!strcmp(refnames->items[i - 1].string, refnames->items[i].string)) {
> +			strbuf_addf(err,
> +				    "Multiple updates for ref '%s' not allowed.",
> +				    refnames->items[i].string);
> +			return 1;
> +		}
> +	return 0;
> +}
> +
>  /* backend functions */
>  int refs_init_db(struct strbuf *err, int shared)
>  {
> @@ -1102,7 +1133,29 @@ int refs_init_db(struct strbuf *err, int shared)
>  int ref_transaction_commit(struct ref_transaction *transaction,
>  			   struct strbuf *err)
>  {
> -	return the_refs_backend->transaction_commit(transaction, err);
> +	int ret = -1;
> +	struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
> +
> +	assert(err);
> +
> +	if (transaction->state != REF_TRANSACTION_OPEN)
> +		die("BUG: commit called for transaction that is not open");
> +
> +	if (!transaction->nr) {
> +		transaction->state = REF_TRANSACTION_CLOSED;
> +		return 0;
> +	}
> +
> +	if (ref_update_reject_duplicates(transaction, &affected_refnames, err)) {
> +		ret = TRANSACTION_GENERIC_ERROR;
> +		goto done;
> +	}
> +
> +	ret = the_refs_backend->transaction_commit(transaction,
> +						   &affected_refnames, err);
> +done:
> +	string_list_clear(&affected_refnames, 0);
> +	return ret;
>  }