Thanks for mentioning this. It seemed odd to me, too, so I spent some time trying to work it out. As a reviewer, I'm not sure how I'm supposed to assess database or API changes without knowing how they're intended to be used. And deploying them independently seems odd, too, especially if you need to roll it all back.
I think in my ideal world there would be a clean history and I could review a PR commit-by-commit. But, you can't just approve a single commit, so there's a tooling problem there. And most CI runs on an entire push rather than individual commits. And increasingly I see devs using git as an offsite backup for whatever change they just made, rather than breaking commits up into logical chunks. In that workflow, squashed merges make the most sense.
It's probably flawed, but the mental model I came up with is each stacked PR collapses into what would have been an individual commit in a clean PR, with the advantage of being able to be reviewed separately from the other changes and forced to clear CI. And then the whole stack becomes what would have been a clean PR in the old model. That, I can kinda see the benefit of. But, merging only part of the stack into trunk is the mental hurdle I can't clear; it'd be like merging only some commits from a PR. It kinda reminds me of when projects used CVS.
I've really only seen stacked PRs used on projects where history is little more than an audit log. I'm keen to see how this gets employed by open source projects. I think there's a disconnect and it's likely I'm not going to really get it until I see it.
I think in my ideal world there would be a clean history and I could review a PR commit-by-commit. But, you can't just approve a single commit, so there's a tooling problem there. And most CI runs on an entire push rather than individual commits. And increasingly I see devs using git as an offsite backup for whatever change they just made, rather than breaking commits up into logical chunks. In that workflow, squashed merges make the most sense.
It's probably flawed, but the mental model I came up with is each stacked PR collapses into what would have been an individual commit in a clean PR, with the advantage of being able to be reviewed separately from the other changes and forced to clear CI. And then the whole stack becomes what would have been a clean PR in the old model. That, I can kinda see the benefit of. But, merging only part of the stack into trunk is the mental hurdle I can't clear; it'd be like merging only some commits from a PR. It kinda reminds me of when projects used CVS.
I've really only seen stacked PRs used on projects where history is little more than an audit log. I'm keen to see how this gets employed by open source projects. I think there's a disconnect and it's likely I'm not going to really get it until I see it.