git cat-file -e "${HASH}^{commit}" || { usage 1>&2; exit 1; }
CHANGELOG_HEADER="$(git show $HASH:debian/changelog | head -1)"
git cat-file -e "${HASH}^{commit}" || { usage 1>&2; exit 1; }
CHANGELOG_HEADER="$(git show $HASH:debian/changelog | head -1)"