How to detect conflict between two git repositories.

Question

To implement github like fork/pull request function in my project, the auto-merge feature need to detect conflict between source/target repository every time while viewing the pull request.

One solution comes to me is to analyze the 'git request-pull' output. Is there any easier method to detect the conflict?

What is being asked here? Are you implementing a merge tool? Or a diff-viewing tool? Or simply curious what `git push` is going to do? — Robert Martin, Apr 24 '12 at 03:03
In github, a non-conflict pull request can be merged just by click a button on web. Since the source/target repository could keep on committing, a detection of conflict is a must in this process. I'm asking a easier way to detect the conflict. — stcatz, Apr 24 '12 at 03:29

score 3 · Answer 1 · edited Apr 16 '15 at 03:17

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I have deleted my previous answer, I didn't understand the question ...

Now here's the shiny new answer:

git merge --ff-only <branch>

If there are no conflicts, it will do a merge. With a conflict, it gives you a message: Not possible to fast-forward. The console return code (echo $?) is 128 in this situation.

edited Apr 16 '15 at 03:17

Drakes

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answered Apr 24 '12 at 07:13

silvio

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This is not relevant much to the question, but is good while merging after fetch. – Chand Priyankara Mar 13 '15 at 12:35

score 1 · Answer 2 · answered Nov 05 '13 at 01:07

We've created a git-conflict-detector that check the latest pushed commit vs all existing branches.

It's a simple single script that is initiated by GitHub WebHook URL and even know to sent an HiChat notification when conflict is detected.

We based our solution on analyzing the git merge --ff-only <branch> output as you can see here

We've open source it so all can enjoy, learn and contribute.

score 0 · Answer 3 · edited May 23 '17 at 11:48

As far as I know, you can't find out if a merge would produce conflicts until you actually merge these branches.

This was already pointed out in: How to test a merge without actually merging first.

So, to answer your question, if you need to implement this kind of feature, you should most likely try to merge your source/target and rollback the merging action (using git reset --hard).

I never used git request-pull, but looking at the output, I don't see any information which could help you resolve your problem. You could probably get the same result using git diff, git wtf, git remote show <name>.

References:

git wtf : https://github.com/michaelklishin/git-wtf
git request-pull : http://progit.org/book/ch5-2.html

score -1 · Accepted Answer · answered Jun 20 '12 at 07:41

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Finally I wrote my own function to detect conflict.

It is quite simple, just fetch all diff lines, and compare if there is same modifications.

answered Jun 20 '12 at 07:41

stcatz

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It would be great to post it here for future reference – CharlesB Jun 20 '12 at 08:07

How to detect conflict between two git repositories.

4 Answers4