Comment by pertymcpert

The LLVM community used this model for years with Phabricator before it was EOL'd and moving to GH and PRs was forced. It's a proven model and works very well in complex code bases, multiple components and dependencies that can have very different reviewer groups. E.g: 1) A foundational change to the IR is the baseline commit 2) Then some tweaks on top to lay the groundwork for uses of that change 3) Some implementation of a new feature that uses the new IR change 4) A final change that flips the feature flag on to enable by default.

Each of these changes are dependent on the last. Without stacked PRs you have o only one PR and reviewing this is huge. Maybe thousands of lines of complex code. Worse, some reviewers only need to see some parts of it and not the rest.

Stacked diffs were a godsend and the LLVM community's number one complaint about moving to GitHub was losing this feature.