Manage properly the exclude-from and link-dest parameters in the rsync command

For the record, we met this unexpected behavior:
* [rsync copies files from working directory in addition to the requested ones](askubuntu.com/questions/112717/rsync-copies-files-from-working-directory-in-addition-to-the-requested-ones)
I have found the solution here:
* [I only want to pass options if the runtime data needs them](http://mywiki.wooledge.org/BashFAQ/050#I_only_want_to_pass_options_if_the_runtime_data_needs_them)