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Closes#16903
## Summary
Check if the current working directory exist. If not, provide an error
instead of panicking.
Fixed a stale comment in `resolve_default_files`.
<!-- What's the purpose of the change? What does it do, and why? -->
## Test Plan
I added a test to the `resolve_files.rs`.
Manual testing follows steps of #16903 :
- Terminal 1
```bash
mkdir tmp
cd tmp
```
- Terminal 2
```bash
rm -rf tmp
```
- Terminal 1
```bash
ruff check
```
## Open Issues / Questions to Reviewer
All tests pass when executed with `cargo nextest run`.
However, with `cargo test` the parallelization makes the other tests
fail as we change the `pwd`.
Serial execution with `cargo test` seems to require [another dependency
or some
workarounds](https://stackoverflow.com/questions/51694017/how-can-i-avoid-running-some-tests-in-parallel).
Do you think an additional dependency or test complexity is worth
testing this small edge case, do you have another implementation idea,
or should i rather remove the test?
---
P.S.: I'm currently participating in a batch at the [Recurse
Center](https://www.recurse.com/) and would love to contribute more for
the next six weeks to improve my Rust. Let me know if you're open to
mentoring/reviewing and/or if you have specific areas where help would
be most valued.
---------
Co-authored-by: Micha Reiser <micha@reiser.io>
d0c8eaa092