Bug 130221

I did extensive tests with drpmsync the last days and found some
bugs/problems/possible improvements:

1. drpmsync client selects a random version for the "have" parameter.  This can
lead to the case that the server sends the full package because he does not have
a delta for this old version (any more) although the client could have provided
a more recent version as well for which a delta would have been availlable on
the server.  In my opinion the client should always send the latest version with
the "have" parameter to the server because it is most likely in that case to get
a short delta file.  Alternatively the protocol could be changed to allow
multiple "have" parameters allowing the server to select the best.

2. It would be useful if the protocol had an option to only ask the server which
patches would be availlable for a specific "have" case without actual transfer
of the delta/rpm but instead transfer only the relative file name of the
delta/rpm.  This would allow a client to fetch the actual file from a faster
server that does not speak drpmsync itself (like gwdg.de). An option could
specify the external source as a URL.

3. An option to dump the fetched contents information to a file would be useful
for debugging. Another option to reuse a dumped file instead of refetching this
information for the server would even add more value when hacking at the tool
because this reduces startup times of the tool dramatically.

4. Do you have a written documentation about the protocol (format of the
requests and answer packages)? Currently I am reading all this information from
the source but this is not very comfortable and specifying a protocol by written
source code is error prone according accidential changes of the protocol and
thus making incompatible versions of the protocol.