Mike Hommey <mh@xxxxxxxxxxxx> writes:
> On Tue, Jul 03, 2018 at 11:41:42AM -0700, Junio C Hamano wrote:
>> Mike Hommey <mh@xxxxxxxxxxxx> writes:
>>
>> > When the reference buffer is empty, diff_delta returns NULL without
>> > really attempting anything, yet fast-import counts that as a delta
>> > attempt.
>>
>> But that is an attempt nevertheless, no? Attempted and failed to
>> find anything useful, that is. What problem are you trying to solve
>> and what issue are you trying to address, exactly?
>>
>> ... goes and reads the patch ...
>>
>> > Signed-off-by: Mike Hommey <mh@xxxxxxxxxxxx>
>> > ---
>> > fast-import.c | 2 +-
>> > 1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/fast-import.c b/fast-import.c
>> > index 4d55910ab9..12195d54d7 100644
>> > --- a/fast-import.c
>> > +++ b/fast-import.c
>> > @@ -1076,7 +1076,7 @@ static int store_object(
>> > return 1;
>> > }
>> >
>> > - if (last && last->data.buf && last->depth < max_depth
>> > + if (last && last->data.len && last->data.buf && last->depth < max_depth
>> > && dat->len > the_hash_algo->rawsz) {
>> >
>> > delta_count_attempts_by_type[type]++;
>>
>> This is a misleading patch as the title and the proposed log message
>> both talk about "attempts are counted but we didn't actually do
>> anything", implying that the only problem is that the counter is not
>> aligned with reality. The fact that the post-context we see here
>> only shows the "counting" part does not help us, either.
>>
>> But the next line in the post-context is actually code that does
>> something important, which is ...
>>
>> delta = diff_delta(last->data.buf, last->data.len,
>> dat->buf, dat->len,
>> &deltalen, dat->len - the_hash_algo->rawsz);
>> } else
>> delta = NULL;
>>
>>
>> ... and makes the reader realize that the change itself is much
>> better than the patch with 3-line context, the title, and the
>> proposed log message advertises it as ;-)
>>
>> How about selling it this way instead?
>>
>> fast-import: do not call diff_delta() with empty buffer
>>
>> We know diff_delta() returns NULL, saying "no good delta
>> exists for it", when fed an empty data. Check the length of
>> the data in the caller to avoid such a call.
>>
>> This incidentally reduces the number of attempted deltification
>> we see in the final statistics.
>>
>> or something like that?
>
> Fair enough. Do you want me to send a v2 with this description?
For a single-patch topic like this one, if you like what was in the
e-mail verbatim, saying so is sufficient, as I can just use the
material to run "git commit --amend". For anything more involved
(e.g. "oh, then insert a code to do this before that function"
and/or a fix to an earlier patch in a multi-patch series), I'd
prefer a re-submission, which can be processed just the same way as
any other new topic.
Thanks.
