Rsync: backup only specified files and preserve relative paths without a parent directory

rsync-preserve-dirs-structure.sh

#!/usr/bin/env bash

#setup
mkdir -p playground/{source,target} && cd playground
mkdir -p source/{a,b,c}/{d,e,f}/{g,h,i}
touch source/{.,a,b/{e,f},c/d/{g,h,i}}/{1,2,3,4,5}

#first sync
cd source && rsync -aR 3 a/ b/f/ c/d ../target/ --delete && cd -
find -type f

#remove a file
echo -n 'Remove a file (source/b/f/3) to check if --delete will work as expected [enter]: '; read cnt
rm source/b/f/3

#second sync
cd source && rsync -aR 3 a/ b/f/ c/d ../target/ --delete && cd -
find -type f