Question

I forked a repository R as R1. Then I make some changes to R1.

B forked the repository R as R2, and R2 becomes the mainly maintained repository.

Now I want to send pull request to R2, how to do?

And what if I want to keep my R1 updated with R2?

Answer 1

To send pull request to R2 you can click Pull Request on R1 (your own fork) page, then Edit and choose R2 repository in base fork section.

To pull updates from R2 and push them to your R1 repository you can add new remote for R2 like that:

git remote add r2 git://github.com/<path-to-r2-on-github>.git

Then you can pull changes from r2/master to your local master like that:

git checkout master # checkout your local master
git pull r2 master  # pull changes from master branch of r2 remote repository

And then push them to your R1 (I assume you have R1 configured as origin remote):

git push origin master # push changes (that you previously pulled from r2) 
                       # from local master to master in R1 repository