Re: [PATCH] diff: resurrect the traditional empty "diff --git" behaviour

[David Kastrup <dak@gnu.org>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> On Fri, 31 Aug 2007, Jeff King wrote:
>
>> On Fri, Aug 31, 2007 at 01:13:42PM -0700, Junio C Hamano wrote:
>> 
>> > If you set diff.autorefreshindex configuration variable, it
>> > squelches the empty "diff --git" output, and at the end of the
>> > command, it automatically runs "update-index --refresh" without
>> > even bothering the user.  In other words, with the configuration
>> > variable set, people who do not care about the cache-dirtyness
>> > do not even have to see the warning.
>> 
>> Nice. This is much more sane behavior, IMHO, and I think it should make 
>> everyone happy.
>
> I could even imagine that this will eventually become the standard 
> behaviour.
>
>> >  Same here.  This patch saw only very light testing, but I
>> >  personally think is a sane thing to do before 1.5.3 final.
>> 
>> Passes my light testing as well, but I have a feeling we just tested the
>> same things...;)
>> 
>> One question on the implementation (and remember that I am somewhat
>> ignorant of the structure of this part of the code, so the answer may be
>> "it's too ugly"): is there a good reason to refresh _after_ the diff?
>
> We do not need to do it always.  After the diff, we know if the
> index needs refreshing.  Before, we don't.

Hm.  At the moment where it is first noticed, it should be still
possible to start a refresh.  Is there a particular gain to be
expected?  One thing I could think of is that when using a pager, the
diff might often die of SIGPIPE before being able to refresh.

>> It seems like when we are looking through the working tree and
>> index the first time, we notice that the stat information doesn't
>> match; why can't we update it then? That would save an extra
>> working tree traversal.
>
> But that would be intrusive in the diff machinery IMHO.  It should
> stay as read-only as possible.

Hm.  Not sure where the gain is in that, if a refresh is done, anyway.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum