#!/bin/bash
set -e
R=~/tmp/bkd
rm -rf $R
mkdir -p $R

# In my home directory, I keep a copy of the original rsync source code.
mkdir -p $R/home/matt/rsync
echo "rsync" >$R/home/matt/rsync/rsync.c

# Soon I plan to make some changes to rsync, and I want $R/home/matt/rsync-test
# to always contain my latest testing version.  But for now, I'm just going to
# make rsync-test a link to plain rsync.  For some reason, I use an absolute
# symlink.
ln -s $R/home/matt/rsync $R/home/matt/rsync-test

# The system is backed up.
rsync -a --exclude="/backup*" $R/ $R/backup1/

# Now I'm ready to make my changes, so I replace the symlink with an actual
# copy of the rsync source code.
rm $R/home/matt/rsync-test
rsync -a $R/home/matt/rsync/ $R/home/matt/rsync-test/

# The system is backed up again.  The admin uses --link-dest to save space.
rsync -a --exclude="/backup*" --link-dest="$R/backup1/" $R/ $R/backup2/

# Rsync incorrectly followed the symlink $R/backup1/home/matt/rsync-test
# => $R/home/matt/rsync in the link-dest dir.  As a result,
# $R/backup2/home/matt/rsync-test/rsync.c is a hard link to $R/home/matt/rsync/rsync.c .
# But for the moment, the backup is still OK.
cat $R/backup2/home/matt/rsync-test/rsync.c

# Now I start making my changes.
echo "rsync with changes" >$R/home/matt/rsync/rsync.c

# Uh-oh!  Look what happened to the backup!
cat $R/backup2/home/matt/rsync-test/rsync.c