[llvm] [mlir] [MLIR] Add debug log to the pass manager (NFC) (PR #156205)

[Andrzej Warzyński via llvm-commits]

banach-space wrote:

> I'm pretty sure this was covered during the migration to GitHub pull-request and this was meant as a suggestion and nothing more, I'll do some digging.

Re-reading [our policy](https://llvm.org/docs/GitHub.html#rebasing-pull-requests-and-force-pushes):

> In general, you should avoid rebasing a Pull Request and force pushing to the branch that’s the root of the Pull Request during the review. This action will make the context of the old changes and comments harder to find and read.
> 
> Sometimes, a rebase might be needed to update your branch with a fix for a test or in some dependent code.

So yes, you were right, this is just a **suggestion** and I guess there is no need to bring this to Discourse (unless anyone reading this feels otherwise).

That said, 
> At least as I recollect, people like me (and others) who were used to the Phabricator flow were quite adamant to not have to change our local workflow to adopt pull-request: that is GitHub quirks aren't a reason to degrade our development experience.

I was also very fond of the Phabricator flow. That's a side point though. I totally understand (and can relate to) that you want to optimise for your **development** experience. However, this comes at a price to **reviewers’** experience in general, especially for folks reading PRs in the future.

> to make this PR part of a stack I have to close the PRs and re-open new ones from branches in the LLVM repo.

That's what I do occasionally and it works fine for me 🤷🏻 Note, however, that in the absence of "user-branches", we [recommend](https://llvm.org/docs/GitHub.html#stacked-pull-requests) a "dependency notes". Let me update the description accordingly. 

https://github.com/llvm/llvm-project/pull/156205