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Re: problems with overloading of the semantics of version number in cygwin/unison

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.



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

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