Re: show all merge conflicts

["G. Sylvie Davies" <sylvie@bit-booster.com>]

On Fri, Jan 27, 2017 at 9:51 AM, Jeff King <peff@peff.net> wrote:
> On Fri, Jan 27, 2017 at 11:56:08AM -0500, Michael Spiegel wrote:
>
>> I'm trying to determine whether a merge required a conflict to resolve
>> after the merge has occurred. The git book has some advice
>> (https://git-scm.com/book/en/v2/Git-Tools-Advanced-Merging) to use
>> `git show` on the merge commit or use `git log --cc -p -1`. These
>> strategies work when the merge conflict was resolved with a change
>> that is different from either parent. When the conflict is resolved
>> with a change that is the same as one of the parents, then these
>> commands are indistinguishable from a merge that did not conflict. Is
>> it possible to distinguish between a conflict-free merge and a merge
>> conflict that is resolved by with the changes from one the parents?
>
> No. You'd have to replay the merge to know if it would have had
> conflicts.
>


Aside from the usual "git log -cc", I think this should work (replace
HEAD with whichever commit you are analyzing):

git diff --name-only HEAD^2...HEAD^1 > m1
git diff --name-only HEAD^1...HEAD^2 > b1
git diff --name-only HEAD^1..HEAD    > m2
git diff --name-only HEAD^2..HEAD    > b2

If files listed between m1 and b2 differ, then the merge is dirty.
Similarly for m2 and b1.

More information here:

http://stackoverflow.com/questions/27683077/how-do-you-detect-an-evil-merge-in-git/41356308#41356308


- Sylvie



> There was a patch series a few years ago that added a new diff-mode to
> do exactly that, and show the diff against what was resolved. It had a
> few issues (I don't remember exactly what) and never got merged.
>
> Certainly one complication is that you don't know exactly _how_ the
> merge was done in the first place (e.g., which merge strategy, which
> custom merge drivers were in effect, etc). But in general, replaying
> with a standard merge-recursive would get you most of what you want to
> know.
>
> I've done this manually sometimes when digging into erroneous merges
> (e.g., somebody accidentally runs "git reset -- <paths>" in the middle
> of a merge and throws away some changes.
>
> You should be able to do:
>
>   git checkout $merge^1
>   git merge $merge^2
>   git diff -R $merge
>
> to see what the original resolution did.
>
> -Peff