For Arch Linux. If you're trying to keep your installed package count under control this might help sort out what you need installed and what was installed by something else.

manual-package-tidy.sh

#!/bin/sh
#
# This script will change any explicity/manually installed packages that are
# dependended on by other packages into packages installed as dependencies. The
# idea is to minimise the manually installed packages throughout upgrades.
#

PACMAN=yaourt
TEMPDIR=$(mktemp -d /tmp/packages.XXXXXXXXXX)

${PACMAN} -Qe > ${TEMPDIR}/manual.lst
${PACMAN} -Qet > ${TEMPDIR}/needed.lst

sort ${TEMPDIR}/manual.lst > ${TEMPDIR}/manual.srt
sort ${TEMPDIR}/needed.lst > ${TEMPDIR}/needed.srt

comm -3 ${TEMPDIR}/manual.srt ${TEMPDIR}/needed.srt | cut -d' ' -f1 | cut -d'/' -f2 > ${TEMPDIR}/really-deps.srt
exit

if [ ! -z $(cat ${TEMPDIR}/really-deps.srt) ]; then
	${PACMAN} --noconfirm --asdeps -S $(cat ${TEMPDIR}/really-deps.srt)
fi

rm ${TEMPDIR}/manual.lst ${TEMPDIR}/needed.lst ${TEMPDIR}/manual.srt ${TEMPDIR}/needed.srt ${TEMPDIR}/really-deps.srt
rmdir ${TEMPDIR}