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 "$GITHUB_TOKEN" ]] && logerr "Please set Github API token in GITHUB_TOKEN environment variable"
[[ -z "$LINEAR_TOKEN" ]] && logerr "Please set Linear API token in LINEAR_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

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 "Found PRs:"
logv "$PRS"
[[ -z "$PRS" ]] && logv "No PRs found in range" && 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"

echo "# Changelog From ${FROM} To ${TO}"
echo ""
echo "## Pull Requests"
echo ""

# Array to store all Linear issues
declare -a ALL_LINEAR_ISSUES

while read -r line; do
  logv "Processing PR line: $line"
  PR_NUM=$(echo $line | sed 's/.*\#\([0-9]*\).*/\1/')
  logv "Extracted PR number: ${PR_NUM}"
  logv "Fetching from https://api.github.com/repos/${PROJECT}/pulls/${PR_NUM}"
  PR_INFO=$(curl -H "Authorization: token $GITHUB_TOKEN" https://api.github.com/repos/${PROJECT}/pulls/${PR_NUM} 2>/dev/null)
  logv "API Response: ${PR_INFO}"

  # Add error handling for GitHub API response
  if [[ -z "$PR_INFO" ]]; then
    logv "Failed to fetch PR #${PR_NUM} info"
    continue
  fi

  # Check if the API returned an error message
  ERROR_MESSAGE=$(echo "$PR_INFO" | jq -r '.message')
  if [[ "$ERROR_MESSAGE" != "null" ]]; then
    logv "GitHub API error for PR #${PR_NUM}: $ERROR_MESSAGE"
    continue
  fi

  PR_TITLE=$(echo "${PR_INFO}" | jq -r '.title')
  if [[ "$PR_TITLE" == "null" || -z "$PR_TITLE" ]]; then
    logv "Invalid PR title for #${PR_NUM}"
    continue
  fi

  logv $PR_TITLE
  if [[ $(echo "$PR_TITLE" | grep -i '^[[:space:]]*release') ]]; then
    logv "Release PR - skipping"
    continue
  fi

  PR_USER=$(echo "${PR_INFO}" | jq -r '.user.login')
  if [[ "$PR_USER" == "null" || -z "$PR_USER" ]]; then
    PR_USER="unknown"
  fi

  PR_MERGED_AT=$(echo "${PR_INFO}" | jq -r '.merged_at')
  if [[ "$PR_MERGED_AT" == "null" || -z "$PR_MERGED_AT" ]]; then
    PR_DATE="unknown"
  else
    if date --version >/dev/null 2>&1; then
      # GNU date (Linux)
      PR_DATE=$(date -d "${PR_MERGED_AT}" +"%Y-%m-%d")
    else
      # BSD date (macOS)
      PR_DATE=$(date -jf '%FT%TZ' "${PR_MERGED_AT}" +"%Y-%m-%d")
    fi
  fi

  echo "<details>"
  echo "<summary>#${PR_NUM} ${PR_TITLE} (@${PR_USER} on ${PR_DATE})</summary>"
  echo ""

  # Add PR description if it exists
  PR_BODY=$(echo "${PR_INFO}" | jq -r '.body')
  if [[ "$PR_BODY" != "null" && ! -z "$PR_BODY" ]]; then
    echo "$PR_BODY" | sed '/^[[:space:]]*$/d'
  fi
  echo "</details>"
  echo ""

  # Look for Linear issue references
  logv "Checking PR body for Linear issues:"
  logv "$PR_BODY"

  CLOSE_LINES=$(echo "$PR_BODY" | grep -iE '[Cc]lose[s]? +OT-[0-9]+')
  logv "Found close lines: $CLOSE_LINES"

  if [[ ! -z "$CLOSE_LINES" ]]; then
    LINEAR_ISSUES=$(echo "$CLOSE_LINES" | grep -oE 'OT-[0-9]+' | sed 's/OT-//')
    logv "Extracted ticket numbers: $LINEAR_ISSUES"
    while read -r issue_number; do
      [[ ! -z "$issue_number" ]] && ALL_LINEAR_ISSUES+=("$issue_number")
    done <<< "$LINEAR_ISSUES"
  fi
done <<< "${PRS}"

# Now process all Linear issues
if [[ ${#ALL_LINEAR_ISSUES[@]} -gt 0 ]]; then
  echo "## Closed Issues"
  echo ""

  # Remove duplicates from ALL_LINEAR_ISSUES
  ALL_LINEAR_ISSUES=($(printf "%s\n" "${ALL_LINEAR_ISSUES[@]}" | sort -u))

  for issue_number in "${ALL_LINEAR_ISSUES[@]}"; do
    logv "Processing Linear issue: OT-${issue_number}"
    QUERY='query($id: String!) { issue(id: $id) { id identifier title url description state { name } creator { displayName } } }'
    VARIABLES="{\"id\": \"OT-${issue_number}\"}"

    LINEAR_RESPONSE=$(curl -s -X POST \
      -H "Content-Type: application/json" \
      -H "Authorization: ${LINEAR_TOKEN}" \
      --data "{\"query\": \"${QUERY}\", \"variables\": ${VARIABLES}}" \
      https://api.linear.app/graphql)

    logv "Linear API Response: ${LINEAR_RESPONSE}"

    ERROR_MESSAGE=$(echo "$LINEAR_RESPONSE" | jq -r '.errors[0].message')
    if [[ ! -z "$ERROR_MESSAGE" && "$ERROR_MESSAGE" != "null" ]]; then
      logv "Linear API error: $ERROR_MESSAGE"
      continue
    fi

    ISSUE_DATA=$(echo "$LINEAR_RESPONSE" | jq -r '.data.issue')
    if [[ "$ISSUE_DATA" != "null" && ! -z "$ISSUE_DATA" ]]; then
      ISSUE_ID=$(echo "$ISSUE_DATA" | jq -r '.identifier')
      ISSUE_TITLE=$(echo "$ISSUE_DATA" | jq -r '.title')
      ISSUE_URL=$(echo "$ISSUE_DATA" | jq -r '.url')
      ISSUE_STATE=$(echo "$ISSUE_DATA" | jq -r '.state.name')
      ISSUE_CREATOR=$(echo "$ISSUE_DATA" | jq -r '.creator.displayName')

      echo "* [${ISSUE_ID}](${ISSUE_URL}) - ${ISSUE_TITLE}"
    fi
  done
fi