generates a changelog from git history, grabbing PRs from github

changelog.sh

#! /bin/bash

COLOR_NC='\033[0m' # No Color
COLOR_LIGHT_GREEN='\033[1;32m'
COLOR_GRAY='\033[1;30m'
COLOR_RED='\033[0;31m'

logv() {
  [[ ! -z "$VERBOSE" ]] && >&2 echo -e "${COLOR_GRAY}$*${COLOR_NC}"
}

logerr() {
  >&2 echo -e "${COLOR_RED}$*${COLOR_NC}"
  exit -1
}

usage() {
  echo "$0 <from> <to>
  Parse the git history to create a changelog from the latest release.

  FROM: the initial commit from which to generate a changelog.
        If 'all', then this will create a complete changelog with
        changes grouped by 'Release*' tag.
        If not given, the merge-base between HEAD and master is assumed.

  TO:   The end commit until which to generate a changelog.
        If not given, 'HEAD' is assumed.
  " && \
  grep " .)\ #" $0; exit 0;
}

while getopts ":hvm" arg; do
  case $arg in
    v) # Verbose mode - extra output
      VERBOSE=true
      FLAGS="$FLAGS -v"
      ;;
    m) # Output in markdown format
      MARKDOWN=true
      ;;
    h | *) # Display help.
      usage
      exit 0
      ;;
  esac
done

shift $(($OPTIND - 1))

[[ -z "$GITHUB_TOKEN" ]] && logerr "Please set Github API token in GITHUB_TOKEN environment variable"
command -v jq >/dev/null 2>&1 || logerr "I require 'jq' but it's not installed."
inside_git_repo="$(git rev-parse --is-inside-work-tree 2>/dev/null)"
[ ! "$inside_git_repo" ] && logerr "fatal: Not a git repository"

TO=$2
[[ -z "$TO" ]] && TO=$(git rev-parse HEAD)

FROM=$1
if [[ -z "$FROM" ]]; then
  mains=("master" "main")
  main=""
  for m in "${mains[@]}"; do
    if git rev-parse --quiet --verify "origin/$m" > /dev/null; then
      main="$m"
    fi
  done
  [[ -z "$main" ]] && logv "no main branch found" && return -1;
  FROM=$(git merge-base "$TO" "origin/$main")
fi

if [[ "$FROM" == "all" ]]; then
  TAGS=$(git tag --sort=-version:refname -l 'Release*')
  LAST=''
  while read -r line; do
    $0 $FLAGS $line $LAST
    [[ $? -ne 0 ]] && exit -1
    LAST=$line
    echo ""
  done <<< "${TAGS}"
  INITIAL=$(git log --reverse --oneline | head -n 1 | awk '{ print $1 }')
  $0 $FLAGS $INITIAL $LAST
  exit $?
fi

FROM=$(git describe --exact-match --tags $FROM 2>/dev/null || echo "$FROM")
TO=$(git describe --exact-match --tags $TO 2>/dev/null || echo "$TO")

logv "git log ${FROM}..${TO}"
PRS=$(git log ${FROM}..${TO} --merges --oneline --grep '^Merge pull request')
logv "$PRS"
[[ -z "$PRS" ]] && exit 0

PROJECT=$(git config --get remote.origin.url | sed -E 's/.*github\.com.(.*)(\.git)?/\1/')
PROJECT=${PROJECT%.git}
logv "Project is ${PROJECT}"
[[ "$PROJECT" == $(git config --get remote.origin.url) ]] && logerr "remote $PROJECT is not a github repo"

ISSUES_FIXED=()

echo "# Changelog From ${FROM} To ${TO}"
while read -r line; do
  PR_NUM=$(echo $line | sed 's/.*\#\([0-9]*\).*/\1/')
  logv "curl https://api.github.com/repos/${PROJECT}/pulls/${PR_NUM}"
  PR_INFO=$(curl -H "Authorization: token $GITHUB_TOKEN" https://api.github.com/repos/${PROJECT}/pulls/${PR_NUM} 2>/dev/null)

  PR_TITLE=$(echo "${PR_INFO}" | jq -r '.title')
  logv $PR_TITLE
  if [[ $(echo "$PR_TITLE" | grep -i '^[[:space:]]*release') ]]; then
    logv "Release PR - skipping"
    continue
  fi

  PR_BODY=$(echo "${PR_INFO}" | jq -r '.body' | sed 's/\\n/\
/g')
  PR_USER=$(echo "${PR_INFO}" | jq -r '.user.login')
  PR_MERGED_AT=$(echo "${PR_INFO}" | jq -r '.merged_at')

  if [[ $(echo "$PR_USER" | grep -i '^dependabot') ]]; then
    logv "Dependabot PR - skipping body"
    PR_BODY=''
  fi

  PR_DATE=$(date -jf '%FT%TZ' "${PR_MERGED_AT}" +"%Y-%m-%d")

  ISSUES_FIXED+=($(echo "$PR_BODY" | grep -i 'fixes\|closes\|refs #' | awk '{print $2}'))

  echo "<details>"
  echo "<summary>#${PR_NUM} ${PR_TITLE} @${PR_USER} merged ${PR_DATE}</summary>"
  echo ""
  echo "${PR_BODY}"
  echo ""
  echo "</details>"
done <<< "${PRS}"

scratch=$(mktemp)
function finish {
  logv rm -rf "$scratch"
  rm -rf "$scratch"
}
trap finish EXIT

for issue in "${ISSUES_FIXED[@]}"
do
  logv "issue: ${issue}"
  ISSUE_NUM=$(echo $issue | sed 's/.*\#\([0-9]*\).*/\1/')
  logv "curl https://api.github.com/repos/${PROJECT}/issues/${ISSUE_NUM}"
  ISSUE_INFO=$(curl -H "Authorization: token $GITHUB_TOKEN" https://api.github.com/repos/${PROJECT}/issues/${ISSUE_NUM} 2>/dev/null)
  [[ -z "$ISSUE_INFO" ]] && continue
  RESP_MESSAGE=$(echo "$ISSUE_INFO" | jq -r .message)
  [[ "$RESP_MESSAGE" == "Not Found" ]] && continue
  logv $ISSUE_INFO
  echo "$ISSUE_INFO" >> $scratch
done

BY_MILESTONE=$(jq --slurp -c 'group_by(.milestone.title) | .[]' $scratch)

echo ""
echo "## Issues closed in this release:"
while IFS= read -r milestone ; do
  milestone_items=$(echo "$milestone" | jq -c '.[]')
  CURRENT_MILESTONE=
  while IFS= read -r ISSUE_INFO ; do
    MILESTONE_URL=$(echo "${ISSUE_INFO}" | jq -r '.milestone.url')
    if [[ "$CURRENT_MILESTONE" != "$MILESTONE_URL" ]]; then
      logv "changing milestone to $MILESTONE_URL"
      CURRENT_MILESTONE="$MILESTONE_URL"
      if [[ "null" == "$MILESTONE_URL" ]]; then
        echo "### No Milestone"
      else
        MILESTONE_TEXT=$(echo "${ISSUE_INFO}" | jq -r '.milestone.title')
        MILESTONE_HTML_URL=$(echo "${ISSUE_INFO}" | jq -r '.milestone.html_url')
        echo "### Milestone: [$MILESTONE_TEXT]($MILESTONE_HTML_URL)"
      fi
    fi

    ISSUE_TITLE=$(echo "$ISSUE_INFO" | jq -r .title)
    ISSUE_USER=$(echo "${ISSUE_INFO}" | jq -r '.user.login')
    ISSUE_NUMBER=$(echo "$ISSUE_INFO" | jq -r .number)
    echo "* #${ISSUE_NUMBER} ${ISSUE_TITLE}"
    echo "  - created by @${ISSUE_USER}"
  done <<< "$milestone_items"
done <<< "$BY_MILESTONE"