[PATCH 1 of 2] contrib: don't hardcode path to bash interpreter

[Olle Lundberg]

# HG changeset patch
# User Olle Lundberg <geek at nerd.sh>
# Date 1395785272 -3600
#      Tue Mar 25 23:07:52 2014 +0100
# Node ID 5c9e0e96192c55a6cd4e468b0f72f8f4d339c82e
# Parent  9a09a625bc93ab69248613abcbea041b785f1a0e
contrib: don't hardcode path to bash interpreter

Use the env binary to figure out the correct bash to use.
Certain systems ships with an ancient version of bash, but the
user might have installed a newer one that is earlier in $PATH.

For example the current version of Mac OS X ships version 3.2.51
of bash, which does not understand new fancy builtins such as
readarray. A user might install a newer version of bash, use that
as their shell and add that path before bin.

diff --git a/contrib/revsetbenchmarks.sh b/contrib/revsetbenchmarks.sh
--- a/contrib/revsetbenchmarks.sh
+++ b/contrib/revsetbenchmarks.sh
@@ -1,6 +1,6 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Measure the performance of a list of revsets against multiple revisions
 # defined by parameter. Checkout one by one and run perfrevset with every
 # revset in the list to benchmark its performance.
 #