git-merge-status

#!/bin/sh
set -eu
    
usage () {
    echo "usage: git merge-status [-h] [<branch>]" >&2
    echo >&2
    echo "Shows merge status of all local branches against branch (defaults to" >&2
    echo "the main branch)." >&2
    echo >&2
    echo "Options:" >&2
    echo "-h    Show this help" >&2
}

while getopts h flag; do
    case "$flag" in
        h) usage; exit 2;;
    esac
done
shift $(($OPTIND - 1))

bulletize () {
    sed -Ee 's/^/  - &/'
}

fail_if_empty () {
    empty=1
    while read line; do
        echo "$line"
        empty=0
    done
    test $empty -eq 0
}

if [ $# -gt 0 ]; then
    base="$1"
else
    base="$(git main-branch)"
fi

echo "Merged into $base:"
if ! git merged "$base" | bulletize | fail_if_empty; then
    echo "(no branches)"
fi

echo
echo "Not merged into $base:"
if ! git merged -u "$base" | bulletize | fail_if_empty; then
    echo "(no branches)"
fi