Re: Designing the filter process protocol (was: Re: [PATCH v3 10/10] convert: add filter.<driver>.process option)

> On 03 Aug 2016, at 20:30, Jakub Narębski <jnareb@gmail.com> wrote:
> 
> ...
> 
> 
> 2. HANDSHAKE (INITIALIZATION)
> 
> Next, there is deciding on and designing the handshake between Git (between
> Git command) and the filter driver process.  With the `filter.<driver>.process`
> solution the driver needs to tell which operations among (for now) "clean"
> and "smudge" it does support.  Plus it provides a way to extend protocol,
> adding new features, like support for streaming, cleaning from file or
> smudging to file, providing size upfront, perhaps even progress report.
> 
> Current handshake consist of filter driver printing a signature, version
> number and capabilities, in that order.  Git checks that it is well formed
> and matches expectations, and notes which of "clean" and "smudge" operations
> are supported by the filter.
> 
> There is no interaction from the Git side in the handshake, for example to
> set options and expectations common to all files being filtered.  Take
> one possible extension of protocol: supporting streaming.  The filter
> driver needs to know whether it needs to read all the input, or whether
> it can start printing output while input is incoming (e.g. to reduce
> memory consumption)... though we may simply decide it to be next version
> of the protocol.