#!/usr/bin/env bash
set -euo pipefail

if [[ $# -ne 2 ]]; then
  printf 'Usage: %s TAG REPOSITORY_URL\n' "$0" >&2
  exit 1
fi

TAG=$1
REPOSITORY_URL=${2%/}
git rev-parse --verify "$TAG^{commit}" >/dev/null
# Start at the parent so the release being built cannot match itself.
PREVIOUS_TAG=$(git describe --tags --abbrev=0 --match 'v[0-9]*' "$TAG^" 2>/dev/null || true)

printf '## Installation / Update\n\n'
printf '```sh\ncurl -fsSL %s/releases/download/%s/install.sh | bash\n```\n\n' "$REPOSITORY_URL" "$TAG"
printf 'The installer is attached to this release. It checks dependencies and verifies binary SHA-256 checksums before installation. Python is not required.\n\n'
printf 'Download `checksums.txt` to verify the attached binaries and `install.sh`.\n\n'
printf '## Changes\n\n'
if [[ -n "$PREVIOUS_TAG" ]]; then
  printf 'Changes since `%s`:\n\n' "$PREVIOUS_TAG"
  git log --no-merges --format='- %s (%h)' "$PREVIOUS_TAG..$TAG"
else
  printf 'Initial release:\n\n'
  git log --no-merges --format='- %s (%h)' "$TAG"
fi