How do I delete a merge from github, permanently?

I accidently merged a project with another project that had nothing to do with it, which I didn't want to do. I successfully unmerged the projects. However, now I 开发者_如何学运维want to delete the erroneous commits. How do I do this.

I tried using git rebase, but it doesn't display the merge.

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If you have already successfully unmerged the projects (which I assume you did through a git reset --hard HEAD~N), then you need to force the changes onto the "mainline" via a:

git push -f

Please note that this isn't generally advised unless you know for sure that no one pulled from the "mainline" after you accidentally made an undesired commit.