[gentoo-user] OT: Copy directories in a special manner

Hi,

 I want to do the following as fast as possible and with less
 system load as possible:

 There are two directories called 'source' and 'target'.

 'source' gets updated via 'svn up', then it gets compiled.
 Since there is no "make install" or similiar, installation
 is done via copying 'source' to 'target'. A symlink from
 /usr/local/bin/<name> to the compiled executabe in (now) 
 'target' completes the installation.

 BUT:
 'source' is a VERY big directory and copying it to 'target'
 after each svn up is a PAIN.

 Now I need a copy mechanism which does the following:
 * copy all files with newer date to 'target' -- this can be done via
   'cp -u'
 * copy all files which only exist in 'source' to 'target' --
   this can be done also with 'cp -u'
 * BUT: Delete all files from 'target' which do not longer exist in 
   'source'

 The last point gives me headaches. Scanning both directory after 
 'cp -u' has done its job may take as long as a "blind copy" from
 'source' to 'target' after 'target' was initially removed.

 Is there any "lean method" to do what is described above ?

 Thank you very much for any help in advance!
 Best regards,
 mcc