Как выбрать между "$0"
и "${BASH_SOURCE[0]}"
Это описание из GNU не очень помогло мне.
BASH_SOURCE
An array variable whose members are the source filenames where the
corresponding shell function names in the FUNCNAME array variable are
defined. The shell function ${FUNCNAME[$i]} is defined in the file
${BASH_SOURCE[$i]} and called from ${BASH_SOURCE[$i+1]}