git-select

#!/usr/bin/env bash

# git select (branch select)
# a git command for checking out a branch or deleting a branch via
# a bash selection menu that uses up/down arrow keys
#
# usage:
# - git select
#
# set up:
# 1) copy the contents of this gist
# 2) create a file that resides in your PATH directory(ies) and name it 'git-select'
#    - you can see your PATH directory(ies) by running 'echo $PATH'
# 3) paste the contents of this gist into the file you just created and save
# 4) make the file an executable by running 'chmod +x path/to/git-select'
#
# this was adapted and renamed from @brybott's original implementation here:
# 
#    https://gist.github.com/brybott/b2752cfb5303ab4c898573327b40a45c
# 
# for added usability, alias gs="git select"
#
##################################################################
##################################################################
# The function select_option is used adapted from:
# https://unix.stackexchange.com/questions/146570/arrow-key-enter-menu
#
# Renders a text based list of options that can be selected by the
# user using up, down and enter keys and returns the chosen option.
#
#   Arguments   : list of options, maximum of 256
#                 "opt1" "opt2" ...
#   Return value: selected index (0 for opt1, 1 for opt2 ...)
#   Side effect: sets $selected and $action for use later
select_option() {
    local del_row=0
    while true; do
        update_status
        # print options by overwriting the last lines
        local idx=0
        for opt; do
            cursor_to $(($STARTROW + $idx))
            if [ $idx -eq $selected ]; then
                print_selected "$opt"
            else
                print_option "$opt"
            fi
            ((idx++))
        done

        # user key control
        action=$(key_input)
        case $action in
            up)    
                ((selected--));
                if [ $selected -lt 0 ]; then selected=$(($# - 1)); fi;;
            down)
                ((selected++));
                if [ $selected -ge $# ]; then selected=0; fi;;
            select|delete|force_delete)
                del_row=1
                break ;;
            quit) 
                exit ;;
        esac
    done
}

##################################################################
##################################################################




branch_selector() {
    ## helper defs
    COLS=$(tput cols)
    ESC=$(printf "\033")

    # little helpers for terminal print control and key input
    cursor_to()        { printf "$ESC[$1;${2:-1}H"; }
    cursor_blink_on()  { printf "$ESC[?25h"; }
    cursor_blink_off() { printf "$ESC[?25l"; }
    get_cursor_row()   { IFS=';' read -sdR -p $'\E[6n' ROW COL; echo ${ROW#*[}; }
    reprint()          { printf "\r% -$((COLS))s" "$@"; }
    print_option()     { reprint "   $1 "; }
    print_selected()   { reprint "  $ESC[7m $1 $ESC[27m"; }

    key_input() { 
        read -s -n1 key
        if [ "$key" == "$ESC" ]; then
            read -sn2 extra
        fi
        case "$key$extra" in
            k|"$ESC[A") echo up;;
            j|"$ESC[B") echo down;;
            q|Q) echo quit;;
            d) echo delete;;
            D) echo force_delete;;
            "") echo select;;
        esac
    }


    # initially print empty new lines (scroll down if at bottom of screen)
    num_branches=$#
    if [ $# -eq 0 ]; then 
        exit 1
    elif [ $num_branches -eq 1 ]; then
        echo "Only one branch to select: $1" 
        exit 1
    fi
    for opt; do printf "\n"; done
    # 1 more for status
    printf "\n"

    # determine current screen position for overwriting the options
    local STATUSROW=`get_cursor_row`
    local LASTROW=$(($STATUSROW - 1))
    local STARTROW=$(($LASTROW - $num_branches))

    local selected=0
    local num_deleted=0
    local last_err=
    local last_err_ts=

    log() {
        last_err="$@"
        last_err_ts=$(date +%s)
    }

    print_status() { 
        cursor_to $STATUSROW
        msg=$(echo $@ | head -c $((COLS)) | tr '\n' ' ')
        reprint "$msg"
    }

    update_status() {
        now=$(date +%s)
        last_ts=${last_err_ts:-$((now-10))}
        if [ $(( $now - $last_ts )) -gt 1 ]; then
            print_status "q: quit | j/k (↑/↓): nav | d/D: delete"
        else
            print_status "$last_err"
        fi
    }

    refresh() {
        cur=`get_cursor_row`
        cursor_to $STARTROW
        n=0; while [ $n -lt $num_branches ]; do ((n++)); reprint ' '; printf '\n'; done

        update_status
        cursor_to $cur
    }

    # ensure cursor and input echoing back on upon a ctrl+c during read -s
    trap "cursor_blink_on; stty echo; cursor_to $STATUSROW; printf '\n'" EXIT

    cursor_blink_off
    local selected=0
    local action=
    
    while true; do 
        refresh
        branches=($(git branch --format='%(refname:short)'))

        # select_option sets `selected` and `action`
        select_option ${branches[@]}

        branch=${branches[$selected]}
        checked_out_branch=$(git branch --show-current)

        case $action in
            select)
                log $(git checkout $branch 2>&1 1>/dev/null); 
                update_status 
                break ;;
            delete|force_delete)
                if [ "$branch" == "master" ]; then
                    log 'Not deleting master branch. Sorry!'; 
                else
                    [ "$branch" == "$checked_out_branch" ] && git checkout master >/dev/null 2>&1
                    flag="-d"
                    [ $action == "force_delete" ] && flag="-D"
                    msg=$(git branch $flag $branch 2>&1 )
                    if [ $? -eq 0 -a $selected -gt 1 ]; then
                        cursor_to $((selected-1))
                    fi
                    log $msg
                fi ;;
            exit)
                break ;;
        esac
    done
}

branch_selector $(git branch --format='%(refname:short)')