$NetBSD: patch-bin_arc,v 1.1 2017/03/30 20:14:16 roy Exp $

commit dcf167cba8294310d03c29b2eec82c2aea8aa9b4
Author: Roy Marples <roy@marples.name>
Date:   Thu Mar 30 12:20:19 2017 +0100

    arcanist: arc should work with any POSIX shell
    
    Summary:
    Currently arc requires bash for `$BASH_SOURCE[0]` and
    substring range removal, both of which are bash specific features.
    
    This patch gets the same result with `$0` and string prefix removal,
    both of are are POSIX features and as such all shells should support.
    
    Fixes T12477.
    
    Test Plan:
      *  Run `bin/arc` on systems with bash and other shells as `/bin/sh`
    
    Reviewers: #blessed_reviewers!
    
    Subscribers: epriestley
    
    Maniphest Tasks: T12477
    
    Differential Revision: https://secure.phabricator.com/D17582

diff --git a/bin/arc b/bin/arc
index e125698b..96f321a3 100755
--- bin/arc
+++ bin/arc
@@ -1,14 +1,16 @@
-#!/usr/bin/env bash
+#!/bin/sh
 
 # NOTE: This file is a wrapper script instead of a symlink so it will work in
 # the Git Bash environment in Windows.
 
-# Do bash magic to resolve the real location of this script through aliases,
+# Do shell magic to resolve the real location of this script through aliases,
 # symlinks, etc.
-SOURCE="${BASH_SOURCE[0]}";
+SOURCE="$0";
 while [ -h "$SOURCE" ]; do
   LINK="$(readlink "$SOURCE")";
-  if [ "${LINK:0:1}" == "/" ]; then
+  # Test if the first character of $LINK is / by removing it from the front
+  # and testing equality
+  if [ "${LINK#/}" != "$LINK" ]; then
     # absolute symlink
     SOURCE="$LINK"
   else