bump-version

#!/usr/bin/env bash

# bump-version [--push] (bump | show)
# bump-version --list-files

set -o nounset
set -o errexit
set -o pipefail

# Stores the canonical version for the project.
VERSION_FILE=version.txt
# Files that should be updated with the new version.
VERSION_FILES=("$VERSION_FILE")

USAGE=$(
  cat << END_OF_LINE
Update the version of the project.

Usage:
  ${0##*/} [--push] (bump | show)
  ${0##*/} --list-files
  ${0##*/} (-h | --help)

Options:
  -h | --help    Show this message.
  --push         Perform a \`git push\` after updating the version.
  --list-files   List the files that will be updated when the version is bumped.
END_OF_LINE
)

old_version=$(< "$VERSION_FILE")
# Comment out periods so they are interpreted as periods and don't
# just match any character
old_version_regex=${old_version//\./\\\.}
new_version="$old_version"

commit_prefix="Bump"
with_push=false

#######################################
# Display an error message, the help information, and exit with a non-zero status.
# Arguments:
#   Error message.
#######################################
function invalid_option() {
  echo "$1"
  echo "$USAGE"
  exit 1
}

#######################################
# Bump the version.
# Arguments:
#   None
# Returns:
#   The new version.
#######################################
function bump_version() {
  local temp_version
  # Set it to the current date in UTC. We must use the -u short option to maintain
  # support with the BSD date command which is used on macOS.
  temp_version=$(date -u +%Y.%m.%d)
  echo "$temp_version"
}

if [ $# -eq 0 ]; then
  echo "$USAGE"
  exit 1
else
  while [ $# -gt 0 ]; do
    case $1 in
      --push)
        if [ "$with_push" = true ]; then
          invalid_option "Push has already been set."
        fi

        with_push=true
        shift
        ;;
      bump)
        shift
        ;;
      show)
        echo "$old_version"
        exit 0
        ;;
      -h | --help)
        echo "$USAGE"
        exit 0
        ;;
      --list-files)
        printf '%s\n' "${VERSION_FILES[@]}"
        exit 0
        ;;
      *)
        invalid_option "Invalid option: $1"
        ;;
    esac
  done
fi

new_version=$(bump_version)

tmp_file=/tmp/version.$$
for version_file in "${VERSION_FILES[@]}"; do
  if [ ! -f "$version_file" ]; then
    echo Missing expected file: "$version_file"
    exit 1
  fi
  sed "s/$old_version_regex/$new_version/" "$version_file" > $tmp_file
  mv $tmp_file "$version_file"
done

git add "${VERSION_FILES[@]}"
git commit --message "$commit_prefix version from $old_version to $new_version"

if [ "$with_push" = true ]; then
  git push
fi