From mboxrd@z Thu Jan  1 00:00:00 1970
From: Neil Horman <nhorman@tuxdriver.com>
Subject: Re: [PATCH v7 4/4] git-rebase: add keep_empty flag
Date: Fri, 20 Apr 2012 06:35:03 -0400
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Cc: Thomas Rast <trast@student.ethz.ch>,
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	git@vger.kernel.org, Clemens Buchacher <drizzd@aon.at>,
	Phil Hord <phil.hord@gmail.com>,
	Junio C Hamano <gitster@pobox.com>
To: Junio C Hamano <jch@google.com>
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On Thu, Apr 19, 2012 at 12:05:56PM -0700, Junio C Hamano wrote:
> Junio C Hamano <jch@google.com> writes:
> 
> > Thomas Rast <trast@student.ethz.ch> writes:
> >
> >> Either way, it should simply be spelled as
> >>
> >> is_empty_commit() {
> >> 	tree=$(git rev-parse "$1"^{tree})
> >> 	ptree=$(git rev-parse "$1"^^{tree})
> >> 	test "$tree" = "$ptree"
> >> }
> >
> > Thanks; will squash in something like this:
> > ...
> 
> Ehh, not like that.  But something like this, as we need to be able to
> pick "root" (t3412 insists on it).
> 
> diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
> index 82042b1..de71543 100644
> --- a/git-rebase--interactive.sh
> +++ b/git-rebase--interactive.sh
> @@ -168,9 +168,11 @@ has_action () {
>  }
>  
>  is_empty_commit() {
> -	tree=$(git rev-parse "$1"^{tree})
> -	ptree=$(git rev-parse "$1"^^{tree})
> -	return $(test "$tree" = "$ptree")
> +	tree=$(git rev-parse "$1"^{tree} 2>/dev/null) ||
> +		die "$1: not a commit that can be picked"
> +	ptree=$(git rev-parse "$1"^^{tree} 2>/dev/null) ||
> +		ptree=4b825dc642cb6eb9a060e54bf8d69288fbee4904
> +	test "$tree" = "$ptree"
>  }
>  
>  # Run command with GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL, and
> 

What about this?
is_empty_commit() {
        tree=$(git rev-parse -q --verify "$1"^{tree})
        ptree=$(git rev-parse -q --verify "$1"^^{tree})

        # Note that if either rev-parse commands fail, the output 
        # of that command will be an empty string.  If that happens
        # We should just return 0, to indicate the commit is non-empty
        # and let the rest of the git rebase logic handle it.
        if test  -z "$tree"  -o  -z "$ptree"
        then
                return 0
        fi

        return test "$tree" = "$ptree"
}