On Sat, Jan 28, 2017 at 6:28 AM, Jeff King <peff@xxxxxxxx> wrote: > On Fri, Jan 27, 2017 at 09:42:41PM -0800, G. Sylvie Davies wrote: > >> 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 > > I don't think that can reliably find evil merges, since it looks at the > file level. If you had one hunk resolved for "theirs" and one hunk for > "ours" in a given file, then the file will be listed in each diff, > whether it has evil hunks or not. > Well, you have to do both. Do "git show -c" to catch that one ("theirs" for one hunk, "ours" for the other, same file). And then do that sequence of the 4 "git diff" commands to identify dirty merges where "theirs" or "ours" was applied to entire files, and thus not showing up in the "git show -c". > I don't think this is just about evil merges, though. For instance, > try: > > seq 1 10 >file > git add file > git commit -m base > > sed s/4/master/ <file >tmp && mv tmp file > git commit -am master > > git checkout -b other HEAD^ > sed s/4/other/ <file >tmp && mv tmp file > git commit -am other > > git merge master > git checkout --ours file > git commit -am merged > > merge=$(git rev-parse HEAD) > > The question is: were there conflicts in $merge, and how were they > resolved? > > That isn't an evil merge, but there's still something interesting to > show that "git log --cc" won't display. > > Replaying the merge like: > > git checkout $merge^1 > git merge $merge^2 > git diff -R $merge > > shows you the patch to go from the conflict state to the final one. > I know the stackoverflow question asks "how to detect evil merges", and I go along with that in my answer. But honestly I prefer to call them dirty rather than evil, and by "dirty" I just mean merges that did not resolve cleanly via "git merge", and had some form of user intervention, be it conflict resolution, or other strange things. The trick I propose with the sequence of 4 "git diff" commands identifies that merge from your example as dirty: $ cat b1 m2 file $ cat b2 m1 file file The trick doesn't really tell you much except that the merge is dirty. If you notice that the "m2" file is empty, I think that's one way to realize that master's edit was dropped, and therefore "other" won. Maybe it even merged cleanly but someone did a "git commit --amend" to make it the merge dirty after the fact. I do like your approach, it's very simple and reliable. But in my situation I'm writing pre-receive hooks for bare repos, so I don't think I can actually do "git merge"! I think my suggestion would work for OP, as long as they also run "git show -c" alongside it. (And your suggestion would work, too, of course). - Sylvie