From mboxrd@z Thu Jan  1 00:00:00 1970
From: Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH] rebase-i: keep old parents when preserving merges
Date: Wed, 16 Jul 2008 14:36:47 -0700
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Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de>,
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To: Stephan Beyer <s-beyer@gmx.net>
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In-Reply-To: <1216173109-11155-1-git-send-email-s-beyer@gmx.net> (Stephan
 Beyer's message of "Wed, 16 Jul 2008 03:51:49 +0200")
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Stephan Beyer <s-beyer@gmx.net> writes:

... Based on the discussion thread, here is a rewrite of the log message.

> When "rebase -i -p" tries to preserve merges of unrelated branches, it
> lost some parents:
>
>  - When you have more than two parents, the commit in the new history
>    ends up with fewer than expected number of parents and this breakage
>    goes unnoticed;
>
>  - When you are rebasing a merge with two parents and one is lost, the
>    command tries to cherry-pick the original merge commit, and the command
>    fails.
>
> Signed-off-by: Stephan Beyer <s-beyer@gmx.net>
>
> diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
> index a35212d..0df7640 100755
> --- a/git-rebase--interactive.sh
> +++ b/git-rebase--interactive.sh
> @@ -174,6 +174,8 @@ pick_one_preserving_merges () {
>  				new_parents="$new_parents $new_p"
>  				;;
>  			esac
> +		else
> +			new_parents="$new_parents $p"
>  		fi
>  	done

Reading the surrounding code, it makes me wonder if you also need to futz
with variables like $preserve and $fast_forward.