From mboxrd@z Thu Jan  1 00:00:00 1970
From: Johannes Sixt <j.sixt@viscovery.net>
Subject: Re: Newbie question regarding 3way merge order.
Date: Mon, 02 Feb 2009 17:10:02 +0100
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Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>
To: "Raimund Berger" <raimund.berger@gmail.com>
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Raimund Berger schrieb:
> do the following conditions hold
> 
> (i)  A+B == B+A for all commits A,B
> (ii) (A+B)+C == A+(B+C) for all A,B,C
> 
> where "+" designates the standard git 3way merge?

I don't think that (ii) does holds in general.

[ In the examples consider each letter/symbol on a line by itself; this
saves vertical space. ]

Start with this (the merge base):

	f(a)

and there are three topic branches growing from here:
A makes this (rename f->g):

	g(a)

B makes this (add another f):

	f(a)f(b)

C makes this (renames a->c):

	f(c)

Then A+B is

	g(a)f(b)

A+C is

	g(c)

B+C is

	f(c)f(b)

(A+B)+C is

	g(c)f(b)

but A+(B+C) is ambiguous:

	g(c)f(b)
or
	f(c)g(b)

-- Hannes