Re: [PATCH v1 1/2] entry.c: update cache entry only for existing files

> From: Lars Schneider <larsxschneider@gmail.com>
> 
> In 2841e8f ("convert: add "status=delayed" to filter process protocol",
> 2017-06-30) we taught the filter process protocol to delay responses.
> 
> That means an external filter might answer in the first write_entry()
> call on a file that requires filtering  "I got your request, but I
> can't answer right now. Ask again later!". As Git got no answer, we do
> not write anything to the filesystem. Consequently, the lstat() call in
> the finish block of the function writes garbage to the cache entry.
> The garbage is eventually overwritten when the filter answers with
> the final file content in a subsequent write_entry() call.
> 
> Fix the brief time window of garbage in the cache entry by adding a
> special finish block that does nothing for delayed responses. The cache
> entry is written properly in a subsequent write_entry() call where
> the filter responds with the final file content.