gh-release-changelog.sh

#!/bin/bash

# This script generates a changelog for a given repository between two versions.
# It uses the GitHub API to fetch all tags and releases, and then generates a changelog
# based on the release notes.
#
# Use it without installation like so:
#
# curl -fsSL https://gist.githubusercontent.com/kopach/53168f97cdf8fa91c0998d44f06d15af/raw/gh-release-changelog.sh | bash -s -- \
#   --repo kopach/karma-sabarivka-reporter \
#   --from v1.1.1 \
#   --to v3.0.2 \
#   --output karma-changelog-v1.1.1-v3.0.2.md
#
# Or save it to a file and run it like so:
#
# bash ./gh-release-changelog.sh --repo kopach/karma-sabarivka-reporter --from v1.1.1 --to v3.0.2 --output karma-changelog-v1.1.1-v3.0.2.md

# Initialize
REPO=""
FROM=""
TO=""
OUTPUT=""
SHOW_HELP=0

# Help text
usage() {
	echo "Usage: $0 [--repo org/repo] [--from v1.0.0] [--to v2.0.0] [--output file.md]"
	echo ""
	echo "Options:"
	echo "  --repo      GitHub repository (e.g. kopach/karma-sabarivka-reporter)"
	echo "  --from      Starting version (older, e.g. v1.1.1)"
	echo "  --to        Ending version (newer, e.g. v3.0.2 )"
	echo "  --output    Output file (optional; if omitted, prints to stdout)"
	echo "  --help      Show this help message"
}

# Parse args
while [[ $# -gt 0 ]]; do
	case "$1" in
	--repo)
		REPO="$2"
		shift 2
		;;
	--from)
		FROM="$2"
		shift 2
		;;
	--to)
		TO="$2"
		shift 2
		;;
	--output)
		OUTPUT="$2"
		shift 2
		;;
	--help)
		SHOW_HELP=1
		shift
		;;
	*)
		echo "❌ Unknown option: $1"
		usage
		exit 1
		;;
	esac
done

if [[ $SHOW_HELP -eq 1 ]]; then
	usage
	exit 0
fi

# Prompt for missing
[[ -z "$REPO" ]] && read -p "Enter repository (e.g. actions/setup-node): " REPO
[[ -z "$FROM" ]] && read -p "Enter FROM version (older, e.g. v1.2.3): " FROM
[[ -z "$TO" ]] && read -p "Enter TO version (newer, e.g. v2.0.0): " TO

echo "🔄 Fetching all git tags from $REPO ..."
ALL_TAGS=($(gh api repos/$REPO/tags --paginate --jq '.[].name'))

# Filter semver tags
SEMVER_TAGS=($(printf '%s\n' "${ALL_TAGS[@]}" | grep -E '^v?[0-9]+\.[0-9]+\.[0-9]+$' | sort -V))

# Validate FROM/TO
if ! printf '%s\n' "${SEMVER_TAGS[@]}" | grep -qx "$FROM"; then
	echo "❌ FROM tag '$FROM' not found in semver tag list."
	exit 1
fi
if ! printf '%s\n' "${SEMVER_TAGS[@]}" | grep -qx "$TO"; then
	echo "❌ TO tag '$TO' not found in semver tag list."
	exit 1
fi

# Build range: FROM → TO (semver)
RANGE_STARTED=0
RANGE_TAGS=()
for TAG in "${SEMVER_TAGS[@]}"; do
	[[ "$TAG" == "$FROM" ]] && RANGE_STARTED=1
	[[ $RANGE_STARTED -eq 1 ]] && RANGE_TAGS+=("$TAG")
	[[ "$TAG" == "$TO" ]] && break
done

if [[ ${#RANGE_TAGS[@]} -eq 0 ]]; then
	echo "❌ No semver tags found between $FROM and $TO."
	exit 1
fi

# Reverse range: TO → FROM
REVERSED_TAGS=($(printf '%s\n' "${RANGE_TAGS[@]}" | tail -r))

# Cache release tags
RELEASE_MAP=$(gh release list --repo "$REPO" --limit 1000 | awk '{print $1}')

# Output setup
print() {
	if [[ -n "$OUTPUT" ]]; then
		echo -e "$1" >>"$OUTPUT"
	else
		echo -e "$1"
	fi
}

# Begin output
[[ -n "$OUTPUT" ]] && echo "💾 Writing changelog to $OUTPUT..."

print "\n📘 Changelog from $TO to $FROM in $REPO:\n"

for TAG in "${REVERSED_TAGS[@]}"; do
	if echo "$RELEASE_MAP" | grep -qx "$TAG"; then
		print "## $TAG"
		BODY=$(gh release view "$TAG" --repo "$REPO" --json body -q '.body')
		print "$BODY"
		print "\n---\n"
	fi
done

[[ -n "$OUTPUT" ]] && echo "✅ Done: changelog saved to $OUTPUT"