Re: using xdl_merge(), was Re: Resolving conflicts

From: Linus Torvalds <torvalds@osdl.org>
Date: Dec 5, 2006, 18:28 UTC
Message-ID: <Pine.LNX.4.64.0612051023460.3542@woody.osdl.org>
In-Reply-To: <4575B32F.5060108@ramsay1.demon.co.uk>

On Tue, 5 Dec 2006, Ramsay Jones wrote:

Show 5 quoted lines

>
> Have you had time to look at my test cases?
> As I said, I found them very useful when debugging
> my git-diff3 code, and (hopefully) you will find them
> to be equally useful.

It might be interesting to also do a simple test:

 - take every single merge in git (or the kernel, if you want even more)

 - ignore all the trivial ones that didn't have any file-level merging at 
   all (ie done entirely in the index)

 - for all the rest, just compare what the end result is when re-doing the 
   merge with "xdl_merge" vs "external 3-way merge".

[ Side note: DO NOT COMPARE AGAINST THE ACTUAL RESULT IN GIT OR IN THE 
  KERNEL ARCHIVE! Those will obviously have been fixed up by humans in the 
  event of a data conflict, and sometimes even in the _absense_ of a data 
  conflict (ie "git commit --amend" to fix up something that got mismerged 
  perfectly automatically or whatever).

  So a script should literally re-do the merge two ways, and compare the 
  end result ]

Is that any "proof"? Of course not. And it will probably show differences due to any conflict handling, but a lot of the time you'd expect to get exactly the same end result, so the occasional differences are going to be just all the more interesting ("it resolved differently, but it was an equally good resolve" is interesting data on its own).

Anybody want to write a small script to do this?