Chore: Pin ruff rule selection

[ModeSevenIndustrialSolutions]

Why

This repository runs the ruff hook with no ruff configuration, so it applies whatever ruff's default rule set happens to be. That default is not stable across releases:

ruff 0.15.22 ->  59 rules across  2 categories (E, F)
ruff 0.16.0  -> 413 rules across 38 categories

A routine pre-commit autoupdate crossing that boundary changes which rules run on code nobody has touched. That is exactly what fails the open autoupdate PR #173 here, on six findings:

Rule	Count	Location
RUF100	2	tests/test_resolve_config_source.py
I001	1	tests/test_resolve_config_source.py
SIM102	1	src/resolve_config_source.py
PIE810	1	src/resolve_config_source.py
PLW1510	1	src/resolve_config_source.py

Deliberately narrow

select = ["E", "W", "F", "C4", "UP"] is the widest set this repository already satisfies, so pinning changes no behaviour today.

It falls short of the organisation superset (E, W, F, I, B, C4, UP) by I and B. I checked both, and each is a code change rather than a configuration one:

• B adds one B904 raise-without-from site at src/resolve_config_source.py:314, which needs a judgement about which exception context to preserve.

• I flags the import block in tests/test_resolve_config_source.py, which deliberately calls sys.path.insert() before importing the module under test. The autofix is only a blank-line removal, but that file is mirrored byte-for-byte with harden-runner-block-action and carries an explicit banner:

  ╔══ SYNCHRONISED FILE — DO NOT EDIT IN ISOLATION ══╗
  Changes must land as paired PRs in both repositories together with the module.

  So it cannot be resolved from this repository alone, and I have deliberately not touched it.

Folding either into a configuration chore would obscure both.

A nice side effect of selecting E: the existing # noqa: E402 on line 30 becomes meaningful again. It is currently unused (hence the two RUF100 findings), because E402 is not enabled under ruff's default.

Note on category-level pinning

Ruff selectors are prefixes, so a future release adding new E* or F* rules will still enable them here. Pinning every rule code individually would be exhaustive and unmaintainable; the aim is to bound the blast radius — 38 categories back to five — not to freeze the set outright.

line-length and target-version are left unset on purpose. Both would change existing behaviour rather than pin it (target-version alters which pyupgrade rules fire).

Validation

• ruff 0.16.0 check src tests → All checks passed!
• ruff 0.15.22 check src tests → All checks passed! (so this is not a one-way door)
• pre-commit run --all-files → every hook passes, including reuse lint on the new file
• No code changes accompany this — configuration only

Unblocks #173.

Related

Paired with the identical change in harden-runner-block-action, which shares the same resolve_config_source module and test file.

[Copilot]

Pull request overview

This PR introduces an explicit Ruff configuration to stabilize lint behavior across Ruff upgrades (notably the default-rule expansion between ruff 0.15.x and 0.16.x) and prevent unrelated pre-commit autoupdate runs from changing which lint rules apply.

Changes:

• Adds a new .ruff.toml that pins lint rule selection to ["E", "W", "F", "C4", "UP"].
• Keeps existing behavior stable by explicitly ignoring E501 and documenting the rationale for future widening via lint.per-file-ignores for tests.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (2)

.ruff.toml:50

• B008 is listed under [lint].ignore, but B rules are not enabled in select, so this ignore is currently redundant and can be confusing to maintainers. Since it has no effect today, consider removing it (it can be re-added when/if B is enabled).

ignore = [
  "E501", # line-too-long: the formatter owns line length
  "B008", # function call in argument default: typer/click idiom
]

.ruff.toml:62

• There appears to be an extra blank line at the end of the file that contains whitespace. This can trip whitespace-cleanup hooks (e.g., trailing-whitespace) and cause pre-commit failures.

"tests/**/*.py" = ["S101", "ARG", "PLR0913", "PLR0917", "PLR2004"]