git-ahead

#!/usr/bin/env sh
_parse_arguments() {
    local    arg
    while (( $# > 0 ))
    do
        arg="$1"
        case "$arg" in
            --submodules)
                _fetch_submodules="--recurse-submodules"
                ;;
            --force)
                _force_fetch="yes"
                ;;
            -*)
                _git_options="${_git_options:-} $arg"
                ;;
            --*)
                _git_options="${_git_options:-} $arg"
                ;;
            *)
                [[ -z ${_target_branch} ]] && _target_branch="$arg"
                ;;
        esac
        shift
    done
    return 0
}

_get_branch_details() {
    _current_branch=$(git rev-parse --abbrev-ref HEAD)
    _tracking_branch=$(git config branch.$_current_branch.merge)
    _tracking_remote=$(git config branch.$_current_branch.remote)
    _tracking_branch_name=${_tracking_branch#"refs/heads/"}
    _remote_url=$(git config remote.$_tracking_remote.url)
}

_fetch_origin_if_needed() {
    _last_fetch=$(git config gitincoming.lastFetch || echo 0)
    _cache_duration=$(git config gitincoming.cacheDuration || echo 3600)
    _current_time=$(date +%s)
    _next_fetch=$((_last_fetch + _cache_duration))
    [[ ${_current_time} -ge ${_next_fetch} ]] && _should_fetch_remote="yes"
    if [[ -n ${_should_fetch_remote} || -n ${_force_fetch} ]]; then
        git fetch ${_fetch_submodules:-"--no-recurse-submodules"} ${_tracking_remote} && git config gitincoming.lastFetch $(date +%s)
    fi
}

_show_remote_log() {
    local binaryName=$(basename $0)
    local actionName=${binaryName#git-}
    case "$actionName" in
        behind)
            git log ${_git_options:-} ..${_tracking_remote}/${_tracking_branch_name}
            ;;
        ahead)
            git log ${_git_options:-} ${_tracking_remote}/${_tracking_branch_name}..
            ;;
    esac
}

_show_local_log() {
    local binaryName=$(basename $0)
    local actionName=${binaryName#git-}
    case "$actionName" in
        behind)
            git log ${_git_options:-} ..${_tracking_branch_name}
            ;;
        ahead)
            git log ${_git_options:-} ${_tracking_branch_name}..
            ;;
    esac
}

_show_target_log() {
    local binaryName=$(basename $0)
    local actionName=${binaryName#git-}
    case "$actionName" in
        behind)
            git log ${_git_options:-} ..${1}
            ;;
        ahead)
            git log ${_git_options:-} ${1}..
            ;;
    esac
}

main() {
    _parse_arguments $@
    _get_branch_details
    # if we have a target branch, compare with that and exit
    [[ -n ${_target_branch:-} ]] && \
        _show_target_log "$_target_branch" && \
        exit $?
    # check if we need to compare against a local branch and exit
    [[ -z ${_tracking_remote} || ${_tracking_remote} == "." ]] && \
        _show_local_log && \
        exit $?
    # otherwise, fetch info and compare against the tracked remote branch
    _fetch_origin_if_needed
    _show_remote_log
}

main $@