lint-commit-messages

#!/usr/bin/env bash
set -euf -o pipefail

# shellcheck source=functions
source "${BASH_SOURCE%/*}/../sanctuary-scripts/functions"

run_custom_script lint-commit-messages "$@"

default_branch="$(get default-branch)"

declare -r -i max_length=72

pull_request_number() {
  git log --grep '^Merge pull request #[1-9]' --pretty=format:%s \
  | cut -d '#' -f 2 \
  | cut -d ' ' -f 1 \
  | sort --numeric-sort --reverse \
  | head -n 1
}

project_name() {
  git config --get remote.origin.url \
  | sed -e 's,^git@github[.]com:,,' -e 's,^https://github[.]com/,,' \
  | cut -d / -f 1
}

branch_name() {
  git rev-parse --abbrev-ref HEAD
}

# Find all commits to be merged, and assert that none of them exceeds
# the character limit. Ignore merge commits to accommodate Travis, which
# makes a merge commit (with a long message) in order to test the result
# of merging the pull request.
if git log --no-merges --format=%s "$default_branch.." | grep ".\\{$max_length\\}." ; then
  fail "At least one commit summary exceeds $max_length-character limit"
  exit 1
fi

# Add a digit to the number of the most recently opened pull request
# merged so far. If the largest number encountered is #42, say, the
# current pull request can safely be numbered between #43 and #999.
message="Merge pull request #9$(pull_request_number | tr '[:digit:]' 9) from $(project_name)/$(branch_name)"
if (( "${#message}" <= max_length )) ; then
  pass "$message (${#message} characters)"
else
  fail "Branch name is too long. Merge commit summary would exceed $max_length characters:"
  echo
  echo "  $message"
  exit 1
fi