git rev-parse --abbrev-ref --symbolic-full-name "$@"

}

# If the checkout is not on the production branch,

# assume maintenance is happening and stop.

if [ "$(git_rev_name HEAD)" != "$PRODUCTION_BRANCH" ]; then

    exit 0

fi

# Abort if the production branch isn't tracking a remote branch.

if ! git_upstream="$(git_rev_name '@{upstream}' 2>/dev/null)"; then

    exit 3

fi

IFS=/ read git_remote git_refspec <<EOF

$git_upstream

EOF

git fetch --quiet --no-tags "$git_remote" "$git_refspec"

if [ "$(git rev-parse "$PRODUCTION_BRANCH")" = "$(git rev-parse "$git_upstream")" ]; then

    exit 0

fi

exitcode=0

git merge --quiet --ff-only "${git_remote}/${git_refspec}"

exit "$exitcode"