How to merge remote changes at GitHub?

You can also force a push by adding the + symbol before your branch name.

git push origin +some_branch

You probably have changes on github that you never merged. Try git pull to fetch and merge the changes, then you should be able to push. Sorry if I misunderstood your question.

See the 'non-fast forward' section of 'git push --help' for details.

You can perform "git pull", resolve potential conflicts, and "git push" the result. A "git pull" will create a merge commit C between commits A and B.

Alternatively, you can rebase your change between X and B on top of A, with "git pull --rebase", and push the result back. The rebase will create a new commit D that builds the change between X and B on top of A.