"cleanup" command to clean up the tmp directory

[GoogleCodeExporter]

When an import or checkin is taking place, the incomplete data is stored under 
tmp/ in the repository directory. If the operation is aborted, the data stays 
in the tmp directory indefinitely. There should be a "cleanup" command to 
delete old files from that directory. 

A manual workaround is to make sure that no boar command is currently running, 
and then simply delete the contents of the tmp directory. 

Automatic cleanup might be implemented in the future, but this item only covers 
an explicit cleanup command.

Original issue reported on code.google.com by ekb...@gmail.com on 1 Sep 2011 at 8:08