Re: [PATCH v5 14/15] convert: add filter.<driver>.process option

[Jeff King <peff@peff.net>]

On Fri, Aug 12, 2016 at 09:33:18AM -0700, Stefan Beller wrote:

> > If the result content is empty then the filter is expected to respond
> > with a success status and an empty list.
> > ------------------------
> > packet:          git< status=success\n
> > packet:          git< 0000
> > packet:          git< 0000  # empty content!
> > packet:          git< 0000  # empty list!
> > ------------------------
> 
> Why do we need the last flush packet? We'd expect as many successes
> as we send out contents? Do we plan on interleaving operation, i.e.
> Git sends out 10 files but the filter process is not as fast as Git sending
> out and the answers trickle in slowly?

There was prior discussion in the thread, but basically, it is there to
be able to signal an error that is encountered midway through sending
the file (i.e., to say "status=error"). If you do not have a final
flush, then you would send nothing, and the receiver would be left
wondering if you were successful, or if it simply did not get your error
report yet.

> > If the filter experiences an error during processing, then it can
> > send the status "error". Depending on the `filter.<driver>.required`
> > flag Git will interpret that as error but it will not stop or restart
> > the filter process.
> > ------------------------
> > packet:          git< status=success\n
> 
> So the first success is meaningless essentially?
> Would it make sense to move the sucess behind the content sending
> in all cases?

No, the first success says "good so far, here's the file content". The
second says "I succeeded in sending you the file content".

You _can_ drop the first one, but it may be more convenient for the
receiver to know up-front that there was a failure.

-Peff