[Unison-hackers] version negotiation

[Tõivo Leedjärv]

On Wed, Jun 30, 2021 at 6:00 PM Greg Troxel <gdt at lexort.com> wrote:
>
>   server sends vesrion string
>
>   server sends first message of existing protocol
>
>   if client wants to do old (because client is old, or because client
>   sees a version < 2.51.5), client speaks old protocol as it used to
>
>   if client is new and sees 2.51.5 or higher, then client knows server
>   can do the negotiation protocol.
[...]

I've now pushed an update at
https://github.com/bcpierce00/unison/pull/507/ (ignore the build
errors, these are CI infra errors).
Conceptually this works as proposed by Greg, but to make it actually
work it relies on tricks with the old protocol. Tricks that the new
versions will notice but old versions will silently process with no
negative side-effects.

Please test with various version/platform/connection combinations if you can.