git-tag-from-changelog-md

#!/bin/sh -eu
# SPDX-License-Identifier: WTFPL
# shellcheck enable=

if [ $# -ne 2 ] || [ "${1-}" = -h ] || [ "${1-}" = --help ]
then
	cat >&2 <<- EOF
		usage: $0 <TAG>

		Read CHANGELOG.md, extract only what's relevant to version TAG
		and create tag TAG with extracted text as tag text.
		Expects CHANGELOG.md in format from <https://keepachangelog.com/en/1.1.0/>
	EOF
	exit 64  # EX_USAGE
fi

tag=$1
changefile=$(mktemp taglog.XXXXXX)
trap 'rm -f "$changefile"' EXIT

awk " \
	BEGIN { take=0 } \
	/^## \[.*\] -/ { take=0 } \
	/^## \[$tag\] -/,/^## \[.*\] -/ { take=1 } \
	take==1 { print } \
	" \
	< CHANGELOG.md \
	> "$changefile"

git tag -a "$tag" -F "$changefile"