Re: Common ancestor in merge diffs?

[Linus Torvalds <torvalds@linux-foundation.org>]

On Mon, 26 Jan 2009, Daniel Barkalow wrote:
>
> I was just doing an annoying merge (I'd reorganized code while other 
> people made changes to it), and I kept having the problem that it was hard 
> to figure out what each side had done. Is there some way to ask git for 
> the diffs between the common ancestor (which is unique in my case, so it's 
> actually useful) and each of the sides of the merge? Ideally, it would 
> give essentially the converse of the --cc diff: first column is -stage 1 
> +stage 2; second column is -stage 1 +stage 3.

Have you tried "gitk --merge [filename]"?

That's usually even more useful - because it doesn't just give a diff, it 
gives the actual commits that caused the conflict. That way you see what 
both sides of a merge tried to do.. It's what I do when encountering 
conflicts on the kernel (where I'm usually not the author of _either_ side 
of the code that causes a conflict), and it really is very powerful.

That said, finding the diffs from the common case is pretty trivial too. 
Just do

	git diff MERGE_HEAD...HEAD [filename]

and you'll get the diff from the common case to the HEAD, and if you 
switch them around, you'll get the diff from the common commit to the 
MERGE_HEAD. Note the _three_ dots.

			Linus