Not sure what you think Emacs does, but it very much uses pull requests. You write/change code, commit it, send emails to a mailing list requesting to incorpora

Not sure what you think Emacs does, but it very much uses pull requests. You write/change code, commit it, send emails to a mailing list requesting to incorporate the code. Just because it's not GitHub doesn't mean it doesn't use pull requests (which predate GitHub, all the way back to Git's first releases in 2005).