- implement use of different intervals as source for cloning
   * use 'woechentlich' if available and no backup exists for 'daily'
   * add 'prefer_latest' to prefer different interval, that's newer than
     ours
   * or add 'prefer_same_interval' instead?
- implement detection of partial backups
3. detect unfinished backups
sven / markierung
   - wie seht der Marker aus?
      -> .ccollect-YEAR-MM-DD.HHmm.pid (like the directory)
   --> assume incomplete, when we did not finish.
   --> means it's complete,when rsync was successful
---> partial implemented in 0.5.2 (commented out)
- do not check by name, but by time
   * is ls -t posix?
   * also check: -p -1
- do sed-time check:
1.2. replace sed?
compare timing:
_echo () { echo "$name $msg" }
and create
_techo () { echo "$timestamp $name $msg" }
perhaps create
_eecho () { _techo "ERROR $msg" }
?