From: Ronnie Sahlberg <sahlberg@google.com>
Date: Mon, 14 Jul 2014 22:20:51 GMT
Subject: Re: [PATCH v20 27/48] sequencer.c: use ref transactions for all ref updates
Message-ID: <CAL=YDWkaW_di822qYsf5iKHqfriTjJm6exMVTpbvBunijqgUmQ@mail.gmail.com>
In-Reply-To: <53BBE2D6.2070809@alum.mit.edu>

On Tue, Jul 8, 2014 at 5:23 AM, Michael Haggerty <mhagger@alum.mit.edu> wrote:
> 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) ||
>

Right.  Fixed.

Thanks.