From: Thomas Rast <trast@student.ethz.ch>
Date: Sun, 15 Aug 2010 19:54:57 GMT
Subject: Re: Confused about "degenerate" combined diff for merge commits
Message-ID: <201008152154.57578.trast@student.ethz.ch>
In-Reply-To: <1jna5yt.1pm42a3uw2yquM%lists@haller-berlin.de>

Stefan Haller wrote:
> However, for some of these merge commits I see diff output such as this:
> 
> diff --cc Src/ClipBoard.cpp
> index 4357ea0,4357ea0..3fad79a
> --- a/Src/ClipBoard.cpp
> +++ b/Src/ClipBoard.cpp
> @@@ -71,7 -71,7 +71,7 @@@ AClipBoard* AClipBoard::SNew(
>   
>   AClipBoard* AClipBoard::SClipBoard()
>   {
> --  static AClipBoard* spClipBoard = SNew();
> ++  static TPtr<AClipBoard> spClipBoard = SNew();
>     return spClipBoard;
>   }
>   
> It looks like both merge parents had an identical diff here, so this is
> not a conflict; why does diff --cc even show this to me?

The --cc output has one column per parent, and if you removed all
other +/-/space columns, then (for that hunk) you'd have a unified
diff with that parent.

So I'd say the above means that both parents had

  static AClipBoard* spClipBoard = SNew();

but your merge result was

  static TPtr<AClipBoard> spClipBoard = SNew();

This is usually called an "evil merge" in git terms: it is introducing
changes that are neither coming from one side, nor part of a benign
merge resolution.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch