#!/usr/bin/env bash

usage() {
    echo 1>&2 "usage: git missing [<first branch>] <second branch> [<git log options>] [[--] <path>...]"
}

if [ "${#}" -lt 1 ]
then
    usage
    exit 1
fi

declare -a git_log_args=()
declare -a branches=()
declare -a pathspec=()
declare parse_path=false

for arg in "$@" ; do

    if [[ $parse_path == true ]]; then
        pathspec+=("$@")
        break
    fi

    case "$arg" in
        --)
            parse_path=true
            ;;
        --*)
            git_log_args+=( "$arg" )
            ;;
        *)
            branches+=( "$arg" )
            ;;
    esac
done

firstbranch=
secondbranch=
if [ ${#branches[@]} -eq 2 ]
then
    firstbranch="${branches[0]}"
    secondbranch="${branches[1]}"
elif [ ${#branches[@]} -eq 1 ]
then
    secondbranch="${branches[0]}"
else
    echo >&2 "error: at least one branch required"
    exit 1
fi

git log "${git_log_args[@]}" "$firstbranch"..."$secondbranch" --format="%m %h %s" --left-right -- "${pathspec[@]}"