Bug#990694: unison -addversionno option broken

[Ken Milmore <ken.milmore@gmail.com>]

Package: unison-2.51+4.11.1
Version: 2.51.3-1

The -addversionno option of unison attempts to invoke the same version of unison on the server as on the client, to prevent version mismatches.

This facility seems to have been broken since Debian has augmented the version number of the binary with the ocaml library version.

Example to reproduce:

----

$touch test.src
$unison -addversionno test.src ssh://localhost/test.dst

Unison 2.51.3 (ocaml 4.11.1): Contacting server...
bash: line 1: unison-2.51: command not found
Fatal error: Lost connection with the server

----

The problem is that "unison-2.51" is invoked over the ssh connection, but the unison package no longer provides a binary or symlink with this name.
It does provide:

/usr/bin/unison-2.51+4.11.1 (binary)
/usr/bin/unison (symlink)

A workaround is to install the symlink manually, e.g.:

$sudo ln -s ../../bin/unison-2.51+4.11.1 /usr/local/bin/unison-2.51

Suggested possible bug fixes:

1) Install an additional /usr/bin/unison-2.51 symbolic link in the package, or

2) Modify the unison source to invoke "unison-2.51+4.11.1" instead of "unison-2.51" when the -addversionno option is supplied (however this might break compatibility with other systems).