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Date: Thu, 06 Jan 2005 10:38:21 -0500
From: Richard Lethin <lethin@reservoir.com>
Organization: Reservoir Labs, Inc.
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To: Max Bowsher <maxb@ukf.net>
CC: cygwin@cygwin.com, unison-users@groups1.vip.scd.yahoo.com
Subject: Re: problems with overloading of the semantics of version number in cygwin/unison
References: <41DD5107.8060002@reservoir.com> <004c01c4f403$6d425740$5308a8c0@robinson.cam.ac.uk>
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Max Bowsher wrote:

> Richard Lethin wrote:
> 
>> There is a problem with the way that cygwin is updating the version
>> numbers for cygwin/unison.  Unison is used to synchronize filesystems;
>> it can cross different operating systems over IP.  The protocol uses the
>> version number to decide whether two processes on different systems will
>> communicate.  2.9.1 is the official released version.  There is a beta
>> version 2.10.2, but it is not widely deployed.  Thus people (like me)
>> will want to use the 2.9.1 version of cygwin's unison.  However, cygwin
>> is numbering its instance of this version 2.9.20-1.  When you try to
>> communicate using cygwin's 2.9.20-1 with a standard 2.9.1 version of
>> unison running on another system, the communication fails after the
>> handshake when it discovers that the cygwin version is "2.9.2 [sic]".
>> Yes, I think that the handshake is truncating the protocol string.
>>
>> Anyway, my suggestion is that cygwin update the version of 2.9.1 that it
>> is distributing, to separate the overloaded concept of version number
>> into a cygwin version number (which could then be arbitrary) and leave
>> the protocol number at 2.9.1
> 
> 
> No, this is nothing to do with cygwin, and everything to do with 
> unnecessary inflexibility in the version checking of unison.
> 
> It would be a very bad thing for Cygwin to distribute a version of 
> unison which lies about which version it is to the other end of the 
> connection.

Sure, it's a bad design choice in unison, but cygwin is using the 
version number in Unison - which means something about the protocol 
version in unison - to mean something about the software release - which 
operationally is not what unison really means.  The result is that 
cygwin unison is broken.

> 
> This is a problem that needs to be addressed upstream of Cygwin.

Whatever.

> 
> Max.
> 

-- 
Richard Lethin
Reservoir Labs, Inc.
+1-212-780-0527 ext. 102
www.reservoir.com

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