From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jonathan Nieder <jrnieder@gmail.com>
Subject: Re: Odd results writing a Git pre-receive hook to syntax check PHP
 files.
Date: Mon, 30 Aug 2010 11:33:02 -0500
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Cc: Michael J Gruber <git@drmicha.warpmail.net>, git@vger.kernel.org
To: Chris Patti <cpatti@gmail.com>
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Chris Patti wrote:

> What if this is the
> first time a new ref is being pushed?  Then, old-ref is 000000 and git
> diff --raw throws up a hairball :)

Can't you check for 0{40} and use $(git hash-object -t tree </dev/null)
in its place?

In general, the "LOW-LEVEL COMMANDS (PLUMBING)" listed on the git man
page are meant to be useful for scripts.  They have simple input and
output formats, they don't try to introduce weird exceptions for user
convenience, the git developers are more conservative about changing
them, and so on.