Re: [PATCH v10 13/44] tag.c: use ref transactions when doing updates

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I have moved the patch to add &err to ref_transaction_begin to the
current patch series.

Please see
https://github.com/rsahlberg/git/tree/ref-transactions

On Mon, May 19, 2014 at 10:16 AM, Ronnie Sahlberg <sahlberg@xxxxxxxxxx> wrote:
> On Sat, May 17, 2014 at 6:09 AM, Michael Haggerty <mhagger@xxxxxxxxxxxx> wrote:
>> On 05/16/2014 07:37 PM, Ronnie Sahlberg wrote:
>>> Change tag.c to use ref transactions for all ref updates.
>>>
>>> Signed-off-by: Ronnie Sahlberg <sahlberg@xxxxxxxxxx>
>>> ---
>>>  builtin/tag.c | 14 ++++++++------
>>>  1 file changed, 8 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/builtin/tag.c b/builtin/tag.c
>>> index c6e8a71..b05f9a5 100644
>>> --- a/builtin/tag.c
>>> +++ b/builtin/tag.c
>>> @@ -548,7 +548,6 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>>>       struct strbuf ref = STRBUF_INIT;
>>>       unsigned char object[20], prev[20];
>>>       const char *object_ref, *tag;
>>> -     struct ref_lock *lock;
>>>       struct create_tag_options opt;
>>>       char *cleanup_arg = NULL;
>>>       int annotate = 0, force = 0, lines = -1;
>>> @@ -556,6 +555,8 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>>>       const char *msgfile = NULL, *keyid = NULL;
>>>       struct msg_arg msg = { 0, STRBUF_INIT };
>>>       struct commit_list *with_commit = NULL;
>>> +     struct ref_transaction *transaction;
>>> +     struct strbuf err = STRBUF_INIT;
>>>       struct option options[] = {
>>>               OPT_CMDMODE('l', "list", &cmdmode, N_("list tag names"), 'l'),
>>>               { OPTION_INTEGER, 'n', NULL, &lines, N_("n"),
>>> @@ -701,11 +702,12 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>>>       if (annotate)
>>>               create_tag(object, tag, &buf, &opt, prev, object);
>>>
>>> -     lock = lock_any_ref_for_update(ref.buf, prev, 0, NULL);
>>> -     if (!lock)
>>> -             die(_("%s: cannot lock the ref"), ref.buf);
>>> -     if (write_ref_sha1(lock, object, NULL) < 0)
>>> -             die(_("%s: cannot update the ref"), ref.buf);
>>> +     transaction = ref_transaction_begin();
>>> +     if (!transaction ||
>>> +         ref_transaction_update(transaction, ref.buf, object, prev,
>>> +                                0, !is_null_sha1(prev), &err) ||
>>> +         ref_transaction_commit(transaction, NULL, &err))
>>> +             die("%s", err.buf);
>>
>> If ref_transaction_begin() fails, then won't err still be empty?  (I
>> know it can't happen, and you know it can't happen, but should the
>> caller have to know that?)  It almost seems like ref_transaction_begin()
>> should have an err parameter, too.
>
> I add an err argument in the next series. I would prefer we let that
> patch remain in the next series to
> avoid unbounded growth of the current one.
>
> Ok ?
>
>
>
>>
>> It's kindof late for this question to pop into my head, but: have you
>> thought about embedding the err strbuf in the transaction object?  I
>> admit it would make the problem with ref_transaction_begin() even worse,
>> but maybe it would be a net win in terms of boilerplate?
>
> I think it is more flexible to allow the caller to manage the lifetime
> of the error buffer independently of the transaction.
> It would allow a caller to free the transaction early but delay
> printing the error message until later.
>
> Or it could be used for a multi transaction caller to use a single err
> buffer for all transactions and finally print
> all errors in a single error() call at the end.
>
> struct strbuf err = STRBUF_INIT;
> ... first transaction (... &err)...
> ... second transaction (... &err)...
> ... third transaction (... &err)...
> error("%s", err.buf);
>
>
>
> Similar to how rsync handles errors:
> sahlberg@sahlberg1:~$ mkdir foo
> sahlberg@sahlberg1:~$ touch foo/foo.1
> sahlberg@sahlberg1:~$ touch foo/foo.2
> sahlberg@sahlberg1:~$ mkdir bar
> sahlberg@sahlberg1:~$ chmod 0500 bar
> sahlberg@sahlberg1:~$ rsync -Pav foo/* bar
> sending incremental file list
> foo.1
>            0 100%    0.00kB/s    0:00:00 (xfer#1, to-check=1/2)
> foo.2
>            0 100%    0.00kB/s    0:00:00 (xfer#2, to-check=0/2)
> rsync: mkstemp "/usr/local/google/home/sahlberg/bar/.foo.1.K7dFIP"
> failed: Permission denied (13)
> rsync: mkstemp "/usr/local/google/home/sahlberg/bar/.foo.2.4WdRsW"
> failed: Permission denied (13)
>
> sent 136 bytes  received 50 bytes  372.00 bytes/sec
> total size is 0  speedup is 0.00
> rsync error: some files/attrs were not transferred (see previous
> errors) (code 23) at main.c(1070) [sender=3.0.9]
>
>
>
>>
>>>       if (force && !is_null_sha1(prev) && hashcmp(prev, object))
>>>               printf(_("Updated tag '%s' (was %s)\n"), tag, find_unique_abbrev(prev, DEFAULT_ABBREV));
>>>
>>>
>>
>>
>> --
>> Michael Haggerty
>> mhagger@xxxxxxxxxxxx
>> http://softwareswirl.blogspot.com/
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