determine-release-branch

#!/usr/bin/env bash

set -euf -o pipefail

function usage {
  cat <<EOF
Return the first release branch matching the provided branch regular expression that contains the provided tag.

Usage:
  $0 <BRANCH REGEXP> <TAG>

Examples:
  $0 '^v(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.x$' v11.3.1
EOF
}

if [[ $# -ne 2 ]]; then
  usage

  exit 2
fi

BRANCH_REGEXP="$1"
TAG="${2#refs/tags/}"

contains="$(git branch -a --contains "tags/${TAG}")"
for branch in ${contains}; do
  branch="${branch#remotes/origin/}";
  echo "Checking branch ${branch} against ${BRANCH_REGEXP}." >&2

  if [[ "${branch}" =~ ${BRANCH_REGEXP} ]]; then
    echo "${branch}";

    exit 0;
  fi;
done

echo "No release branch found for tag ${TAG} matching ${BRANCH_REGEXP}. Exiting." >&2
echo "Branches containing tag ${TAG}:" >&2
echo "${contains}" >&2
exit 1