git-clog

#!/bin/bash
set -e

print_usage() {
  cat << EOM
Usage: $(basename $0) [options] [revision-range]

Outputs a summarized list of changes in the revision-range.

Optimized for retrieving Assembla-specific information from git logs
such as ticket or merge request URLs. Also formats squashed merge commits
so that the title of the merge request is used as the changelog.

Options
  -o <format>             The output format (default=changes).
  -v                      Enables verbose output.
  -h                      Displays this message.

Output formats
  commits                 Hash identifiers for the commits.
  changes                 Log of the changes.
  tickets,ticket          Referenced Assembla ticket numbers.
  ticket_urls,urls        URLs to the referenced tickets.
  merge_requests,mr       URLs to the merge requests.

Examples
  Prints a list of changes since the last tag:

    $(basename $0)

  Prints a list of tickets impacted between bug/1234 and master:

    $(basename $0) -o tickets bug/1234..master
  
  Prints URLs of tickets impacted between two specific commits:

    $(basename $0) -o urls 90bb49b..be98809

Environment variables
  GIT_PREVIOUS_SUCCESSFUL_COMMIT
    If revision-range is not specified, the range will default to changes since
    this value (this is populated automatically by Jenkins). If empty,
    the range will default to changes since the most recent tag.
  
  ASSEMBLA_SPACE_URL
    The base Assembla space URL. If empty, this will attempted to be
    derived based on the git remote URL.

See also
  Selecting a range of revisions
    https://git-scm.com/book/en/v2/Git-Tools-Revision-Selection

Authors
  Daniel Pfeiffer, Float (https://gowithfloat.com)
EOM
}

abort() {
  >&2 echo "$(tput setaf 1)$1$(tput sgr0)"
  >&2 echo ""
  print_usage 1>&2
  exit 1
}

output="changes"

while getopts ":o:hv" opt; do
  case ${opt} in
    o)
      output=$OPTARG
      ;;
    v)
      verbose=true
      ;;
    h)
      print_usage
      exit 0
      ;;
    \?)
      abort "Invalid option: -$OPTARG"
      ;;
    :)
      abort "-$OPTARG requires an argument"
      ;;
  esac
done
shift $((OPTIND -1))

info() {
  if [ $verbose ]; then
    >&2 echo "$(tput setaf 3)$1$(tput sgr0)"
  fi
}

guess_space_url(){
  info "Guessing at space URL based on git remote"

  #
  # The Assembla space URL can _probably_ be guessed from the git remote.
  # The git remote will include the space name and could appear in one
  # of the following formats:
  #
  #   git@git.assembla.com:portflio/space-name.label.git
  #   git@git.assembla.com:space-name.label.git
  #
  remote=$(git remote -v | grep fetch | awk '{print $2}')
  repo=${remote##*[:/]}
  space=${repo%%.*}

  if [ -z $space ]; then
    info "Failed to determine Assembla space from remote: ${remote}"
    exit 1
  fi

  space_url="https://app.assembla.com/spaces/${space}"

  info "git repo: ${repo}"
  info "Resolved Assembla space URL: ${space_url}"
  
  echo "$space_url"
}

# The default range of commits will be changes since
# GIT_PREVIOUS_SUCCESSFUL_COMMIT or the most recent tag.
recent_tag=$(git describe --abbrev=0 --tags 2>/dev/null) || true
default_range_start=${GIT_PREVIOUS_SUCCESSFUL_COMMIT:-$recent_tag}
if [ -n "$default_range_start" ]; then
  default_range=$default_range_start..HEAD
fi
range=${1:-$default_range}
space_url=${ASSEMBLA_SPACE_URL:-$(guess_space_url)}

get_commits(){
  # List hashes in reverse order (oldest first) and skips over merge commits.
  git log $range --pretty=format:'%H' --reverse --no-merges
}

# When assembla squashes a merge, the commit messages look like the following.
# To make the list of changes useful, the log message for squash merge commits
# should come from the first line of the body instead of the summary.
#
# Example:
#
#   Merge branch 'bug/various' into 'master'
# 
#   Avoids handling “double navigation” (re #1708)
#
#   done #1707, #1708
#
#   +1: John Doe
#
#   Merged-on: https://assembla.com/code/space-name/git/merge_requests/1234567
#
get_change(){
  if is_merge_commit $1; then
    info "[$1] Using first line of body"
    git show --quiet $1 --pretty=format:'%b' | head -n 1
  else
    info "[$1] Using summary"
    git show --quiet $1 --pretty=format:'%s%n'
  fi
}

is_merge_commit(){
  # Assembla includes the string "Merged-on" when it creates a merge commit.
  # A merge commit is created when a merge request is squashed before merging.
  if [[ $(git show --quiet $1) == *"Merged-on"* ]]; then
    return 0
  fi

  return 1
}

get_mr_url(){
  git show --quiet $1 | grep "Merged-on" | sed 's/.*Merged-on: \(.*\)/\1/'
}

get_tickets(){
  for string in $(git show --quiet $1)
  do
    if [[ $string =~ \#[0-9]+ ]]; then
      echo "${BASH_REMATCH[0]}"
    fi
  done
}

get_ticket_url(){
  while read ticket
  do
    if [ -n "$space_url" ]; then
      echo "${space_url}/tickets/${ticket/\#/}"
    else
      echo $ticket
    fi
  done
}

info "Outputting $range as $output..."

for commit in $(get_commits); do
  case ${output} in
    commits)
      echo $commit
      ;;
    changes)
      get_change $commit
      ;;
    ticket|tickets)
      get_tickets $commit | sort -u
      ;;
    urls|ticket_urls)
      get_tickets $commit | get_ticket_url | sort -u
      ;;
    mr|pr|merge_requests)
      get_mr_url $commit
      ;;
    *)
      error "Invalid output format: $output"
      ;;
  esac
done