Rsync delete orphan files from target only - no copy

Calling Rsync in the following way, using --existing, --ignore-existing and --delete enables the following:

• Only files at target that do not exist at source will be deleted.
• Skipping all file copy operations from source to target.

$ rsync -ri \
  --delete --existing --ignore-existing --progress \
  /path/to/source/ /path/to/target