How to create a github pull request from a forked repository back to the original repository using the github API?

In git/github I want to propose a change to a single file.

To do so, I

fork the repository
clone the repository locally
make the changes and the commit on a new feature branch
push the feature branch to my forked repo
create and merge a pull request to merge the changes from the feature branch to master

Now how can I programatically (via API) create a new pull request to merge the changes I have put in the forked repo to the original repo? How to do that?

The documentation only seems to handle the case when it is the same repository.

Solution

The documentation can be confusing. The following request will create a new pull request on FORKOWNER/THEREPO to merge FORKER:newbranch into FORKOWNER:main:

curl -X POST -H "Accept: application/vnd.github.v3+json" \
  https://api.github.com/repos/FORKOWNER/THEREPO/pulls \
  -d '{"title":"XYZ", "body":"ABC", "head":"FORKER:newbranch", "base":"main"}'

This can also be done with the gh api command of the GitHub CLI:

gh api --method POST -H "Accept: application/vnd.github.v3+json" \
  repos/FORKOWNER/THEREPO/pulls \
  -f title='XYZ' -f body='ABC' -f head='FORKER:newbranch' -f base='main'

Or directly with the gh pr create command of the GitHub CLI:

gh pr create --repo FORKOWNER/THEREPO \
  --title "XYZ" --body "ABC" --head FORKER:newbranch --base main