is it possible to track files in a log to "know" if a file is deleted when syncing next time with --update? something like --read-write-list=file to first read and after work refresh a list of files. if we have such list, we can additionaly check, which files are changed on both sides. has something to do with no. 2131 "Create db files for local/remote directory listing" ...
This is not really rsync's purpose. There are other packages that attempt to do a two-way synchronization of files, such as unison and a perl-script wrapper for rsync named drsync.