One thing that sounds very nice about Github are merge queues: Once your PR is ready, rather than merging, you submit it to the merge queue, which will rebase it on the last PR also on the merge queue. It then runs the CI on each PR, and finally merges them automatically once successful. If CI fails, doesn't get merged, and the next PR skips yours on the chain.
Still a lot of computation & some wait time, but you can just click & forget. You can also parallelize it; since branches are rebased on each other, you can run CI in advance and, assuming your predecessor is also successful, reuse the result from yours.
That sounds roughly like what happens for Rust. I write a Rust PR, somebody reviews it, they have feedback, I modify the PR, they're happy, and it passes to bors (originally: https://github.com/graydon/bors) which then tries to see whether this can be merged with Rust and if so does so.
It is nice to know that if humans thought your change is OK, you're done. I've only committed small changes (compiler diagnostics, documentation) nothing huge, so perhaps if you really get up in it that's more work, but it was definitely a pleasant experience.
... and sure enough it turns out that work on one of the bors successors was in fact discontinued because you should just use this GitHub feature. TIL.
Still a lot of computation & some wait time, but you can just click & forget. You can also parallelize it; since branches are rebased on each other, you can run CI in advance and, assuming your predecessor is also successful, reuse the result from yours.
Only available for enterprise orgs though.