预测功能分支在主分支中合并时的合并冲突

Question

Assume I have a master branch and 3 feature branches. At the end of a sprint all those features are ready and I want to merge them all to the master.

merge feature1 into master => OK
merge feature2 into master => OK
merge feature3 into master => CONFLICTS!

No commits were added to the master but there is still a merge conflict because feature3 conflicts with feature1 and/or feature2.

Is there is tool to predict this merge conflict (to see which feature branches will create merge conflict)? If I could predict this, I could dicede to only merge feature1 and feature3 into the master branch.

Thanks!

Answer 1

The way to predict a merge conflict is to do the merge. ¹ Use a temporary branch to do this:

git checkout -b test master
git merge feature1
git merge feature2
git merge feature3

If everything has gone well, the merges work. You can now, if you like, use this final merge as the result for master itself, by doing a fast-forward operation to move master up to match test :

git checkout master
git merge --ff-only test   # --ff-only means "fail if fast-forward is not possible"

or simply delete branch test if you don't want to do this and/or the merge failed. If the merge failed, use git merge --abort to back out of it, as in footnote 1, or git reset --hard (which does the same thing). Then use git checkout master and git branch -D test :

git merge --abort          # if needed
git checkout master
git branch -D test

The only reason to use a separate test branch above is to avoid having master move until we've done all three merges. But since branch names are private to each repository, there's never any requirement to do this: you can just do the merges, and then roll back (with git reset --hard ) to a previous state if you don't like the result. Just don't git push the commits, or make them available to git fetch , until you have the result you like.

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¹ You can do a test merge without committing, if you like, then use git merge --abort to pretend you never ran the test. But this doesn't work when you need to do more than one merge, as in the case in your question.

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Octopus merges

There is another option, though, which Git calls octopus merges . (Note: You cannot do these using GitHub, and probably not with some other web interfaces.) To do an octopus merge that combines all three features into master at once:

git checkout master
git merge feature1 feature2 feature3

If there are any conflicts, the octopus merge will fail.

(I have never actually used octopus merges in real work. They don't achieve anything you cannot do with regular merges, and people find them confusing, so I tend to stick with the regular merges.)