prepare-commit-msg

#!/usr/bin/env bash
#
# Prepare the commit message by adding a release note.

set -euo pipefail

if [[ "${2-}" = "message" ]]; then
  # This git command is non-interactive so it will not filter out any comments
  # we add. There is nothing more for us to do.
  exit 0
fi

give_up() {
  echo "prepare-commit-msg: $@" >&2
  exit 0  # exit with successful status to allow the commit to proceed
}

# Git can be configured to use any character as the comment indicator. See the
# core.commentChar Git option. We can deduce what comment character is in effect
# by looking for text that we know will be preceded by the comment character.
if ! cchar=$(grep "^. Please enter the commit message for your changes." "$1" | head -c1); then
  give_up "unable to determine comment char"
fi

if ! tempfile=$(mktemp); then
  give_up "failed to create temporary file"
fi
trap "rm -f $tempfile" EXIT

# Inject commit message recommendations into the commit message help text.
sed_script="/$cchar.*an empty message aborts the commit./a\\
$cchar\\
$cchar Commit message recommendation:\\
$cchar\\
$cchar     ---\\
$cchar     <pkg>: <short description>\\
$cchar\\
$cchar     <long description>\\
$cchar\\
$cchar     Release note (category): <release note description>\\
$cchar     ---\\
$cchar\\
$cchar Wrap long lines! 72 columns is best.\\
$cchar\\
$cchar The release note must be present if your commit has user-facing\\
$cchar changes. Leave the default above if not.\\
$cchar\\
$cchar Categories for release notes:\\
$cchar     - cli change\\
$cchar     - sql change\\
$cchar     - admin ui change\\
$cchar     - general change (e.g., change of required Go version)\\
$cchar     - build change (e.g., compatibility with older CPUs)\\
$cchar     - enterprise change (e.g., change to backup/restore)\\
$cchar     - backwards-incompatible change\\
$cchar     - performance improvement\\
$cchar     - bug fix\\
"

# Add an explicit "Release note: None" if no release note was specified.
if ! grep -q '^Release note' "$1"; then
	sed_script+="
;/$cchar Please enter the commit message for your changes./i\\
\\
Release note: None\\
"
fi

if ! sed "$sed_script" "$1" > "$tempfile"; then
  give_up "unable to inject commit message recommendations"
fi

if ! mv "$tempfile" "$1"; then
  give_up "failed overwriting commit message file"
fi