x.py fmt: logic for "which files changed" is broken when there are no changes

[RalfJung]

When I run ./x.py fmt in a clean checkout, I get the following:

fmt: formatted 5534 modified files

If I now change a single file manually, it says instead:

fmt: formatted modified file library/core/src/ptr/mod.rs

Cc @rust-lang/bootstrap

[ibilalkayy]

I modified the same mod.rs file and got this kind of result.

I want to know what is the problem that you want to solve. I didn't understand from this issue that you raised.

[RalfJung]

I want to know what is the problem that you want to solve

• Put your repo into a state where it is entirely in sync with upstream master
• run ./x.py fmt

That should only format the files that changed, which is 0 files. Instead it formats >5000 files.

[RalfJung]

It's not just "no changes" where this case hits, I've also now hit this in a branch that does have changes compared to master. Not sure how to reproduce that.

[ibilalkayy]

I have synced with the upstream master but it showing me all the files.

[Kobzol]

(Note that this issue is not fixed yet, it needs #130161 to be merged first).

[ibilalkayy]

Thank you, for letting me know!