#!/bin/sh
# This file is a part of Julia. License is MIT: https://julialang.org/license

# both $1 and $2 are absolute paths beginning with /
# returns relative path to $2/$target from $1/$source

proc relpath {
    test $Argc -ge 1 && test $Argc -le 2 || return 1
    setvar current = "${2:+"$1"}"
    setvar target = "${2:-"$1"}"
    test $target != . || setvar target = '/'
    setvar target = ""/${target##/}""
    test $current != . || setvar current = '/'
    setvar current = "${current:="/"}"
    setvar current = ""/${current##/}""
    setvar appendix = "${target##/}"
    setvar relative = ''''
    while appendix="${target#"$current"/}"
        [ "$current" != '/' ] && [ "$appendix" = "$target" ]; {
        if test $current = $appendix {
            setvar relative = "${relative:-.}"
            echo ${relative#/}
            return 0
        }
        setvar current = "${current%/*}"
        setvar relative = ""$relative${relative:+/}..""
    }
    setvar relative = ""$relative${relative:+${appendix:+/}}${appendix#/}""
    echo $relative
}
relpath @ARGV