Reorder: first check if we should take all sources, then execute pre-exec

doc/CHANGES

@@ -1,6 +1,7 @@
 0.5.2 to 0.5.3:
    * add 'exec-after-rm' (source specific) configuration
    * added logwrapper
+   * Always print return code of rsync
 
 0.5.1 to 0.5.2:
    * Display correct error code, if rsync returns non-zero

doc/todo/0.6

@@ -45,5 +45,7 @@ Documentation:
    - german doc?
    - exit pre/post exec -> error codes (after implementation!) (in 0.4)
    - write about fast changing fs
-
+- Variables:
+   source_$n
+   no_sources