Pull requests predate Git. The kernel developers used them in the Bitkeeper days:
I exported this a patch and then imported onto a clone of Marcelo's
tree, so it appears as a single cset where the changes that got un-done
never happened. I've done some sanity tests on it, and will test it
some more tomorrow. Take a look at it and let me know if I missed
anything. When Andy is happy with it I'll leave it to him to re-issue a
pull request from Marcelo.
I do not know to what extent Bitkeeper had browser-based workflows. Moving cross-repository merges away from the command line may actually have been innovative, but of course of little interest to kernel developers.