[binhvq]

Fixes #356.

fold_file_name_case always used Unicode lowercasing, so É and é were the same name with --ignore-file-name-case even in the C locale, where GNU only folds ASCII letters.

It now checks LC_CTYPE with the existing is_posix_locale (LC_ALL > LC_CTYPE > LANG, C when unset) and folds ASCII only in the POSIX locale. Exit status matches GNU diff 3.12 for the locale combinations in the test.

Unix only: on Windows these variables are normally unset, and I didn't want to change the folding there.

[codspeed]

Merging this PR will degrade performance by 4.61%

2 warnings

⚠️ 24 benchmarks are dominated by system calls

System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.

Learn more about system calls

See affected benchmarks

⚠️ 1 benchmark with a significant change ran on different hardware

Its base and head results were measured on machines with a different CPU, core count or memory, so the change might not come from the code. Run base and head on the same runner type.

Learn more about Macro Runners

See affected benchmarks

❌ 1 regressed benchmark
✅ 25 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	cmp_parser	10.3 µs	10.8 µs	-4.61%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing binhvq:ignore-case-ascii-in-c-locale (2cf1c17) with main (5a55160)¹}

Footnotes

1. No successful run was found on main (854d777) during the generation of this report, so 5a55160 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[binhvq]

The CodSpeed result looks like noise: the only change is in fold_file_name_case, which the cmp parser never calls, and the report flags cmp_parser as run on different hardware.