Re: [PATCH v20 27/48] sequencer.c: use ref transactions for all ref updates

[Michael Haggerty <mhagger@alum.mit.edu>]

On 06/20/2014 04:43 PM, Ronnie Sahlberg wrote:
> Change to use ref transactions for all updates to refs.
> 
> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
> Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
> ---
>  sequencer.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/sequencer.c b/sequencer.c
> index 0a80c58..fd8acaf 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -272,23 +272,31 @@ static int error_dirty_index(struct replay_opts *opts)
>  static int fast_forward_to(const unsigned char *to, const unsigned char *from,
>  			int unborn, struct replay_opts *opts)
>  {
> -	struct ref_lock *ref_lock;
> +	struct ref_transaction *transaction;
>  	struct strbuf sb = STRBUF_INIT;
> -	int ret;
> +	struct strbuf err = STRBUF_INIT;
>  
>  	read_cache();
>  	if (checkout_fast_forward(from, to, 1))
>  		exit(1); /* the callee should have complained already */
> -	ref_lock = lock_any_ref_for_update("HEAD", unborn ? null_sha1 : from,
> -					   0, NULL);
> -	if (!ref_lock)
> -		return error(_("Failed to lock HEAD during fast_forward_to"));

I think you've changed the semantics when unborn is set.  Please note
that lock_any_ref_for_update() behaves differently if old_sha1 is NULL
(when no check is done) vs. when it is null_sha1 (when it verifies that
the reference didn't previously exist).  So when unborn is true, the old
code verifies that the reference previously didn't exist...

>  
>  	strbuf_addf(&sb, "%s: fast-forward", action_name(opts));
> -	ret = write_ref_sha1(ref_lock, to, sb.buf);
> +
> +	transaction = ref_transaction_begin(&err);
> +	if (!transaction ||
> +	    ref_transaction_update(transaction, "HEAD", to, from,
> +				   0, !unborn, &err) ||

...whereas when unborn is true, the new code does no check at all.  I
think you want

    ref_transaction_update(transaction, "HEAD",
                           to, unborn ? null_sha1 : from,
                           0, 1, &err) ||

> +	    ref_transaction_commit(transaction, sb.buf, &err)) {
> +		ref_transaction_free(transaction);
> +		error("%s", err.buf);
> +		strbuf_release(&sb);
> +		strbuf_release(&err);
> +		return -1;
> +	}
>  
>  	strbuf_release(&sb);
> -	return ret;
> +	ref_transaction_free(transaction);
> +	return 0;
>  }
>  
>  static int do_recursive_merge(struct commit *base, struct commit *next,
> 

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/