[bash] How can I get the source directory of a Bash script from within the script itself?

I would use something like this:

# Retrieve the full pathname of the called script
scriptPath=$(which $0)

# Check whether the path is a link or not
if [ -L $scriptPath ]; then

    # It is a link then retrieve the target path and get the directory name
    sourceDir=$(dirname $(readlink -f $scriptPath))

else

    # Otherwise just get the directory name of the script path
    sourceDir=$(dirname $scriptPath)

fi