some more bashisms fixed...

hooks/common/gl-pre-git.hub-sample

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 # sample pre-git hook to print pending hub requests
 

hooks/common/post-receive.mirrorpush

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 # gitolite mirroring
 

hooks/common/update.secondary.sample

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 # driver script to run multiple update "hooklets".  Each "hooklet" performs a
 # specific (possibly site-local) check, and they *all* have to succeed for the