pathchk: reject an empty file name in portability modes to match GNU

[AlejandroCoronadoN]

In pathchk's portability modes (-p, -P, --portability), an empty file name diverges from GNU:

• -P prints pathchk: '': No such file or directory (it runs the filesystem check first and never reaches the empty-name check).
• -p and --portability print empty file name without the pathchk: prefix.

GNU rejects an empty file name in any portability mode before touching the filesystem, always as pathchk: empty file name:

$ pathchk -P ''             # pathchk: '': No such file or directory   (GNU: pathchk: empty file name)
$ pathchk -p ''             # empty file name                          (GNU: pathchk: empty file name)
$ pathchk --portability ''  # empty file name                          (GNU: pathchk: empty file name)

This adds the early empty-name check (using the existing localized string) for all portability modes. Default mode (pathchk '') is unchanged.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/dd/no-allocate is now passing!
Congrats! The gnu test tests/tail/tail-n0f is now passing!

[cakebaker]

This change makes the "empty file name" checks in check_basic and check_extra unreachable if an empty file name is provided and so you can remove them.

[cakebaker]

You can remove this test as it tests the same as your test, though your test is better.

[codspeed-hq]

Merging this PR will regress 1 benchmark

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
❌ 1 regressed benchmark
✅ 176 untouched benchmarks
⏩ 229 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	du_deep_tree[(100, 3)]	2.3 ms	2.3 ms	-3.42%
⚡	Simulation	du_wide_tree[(5000, 500)]	20.2 ms	19.5 ms	+3.8%

Tip

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

---

_{Comparing AlejandroCoronadoN:pathchk-empty-name-portability (fa12706) with main (a9b64fc)²}

Footnotes

1. 229 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (71ebb92) during the generation of this report, so a9b64fc was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[codspeed-hq]

Unable to generate the performance report

There was an internal error while processing the run's data. We're working on fixing the issue. Feel free to contact us on Discord or at support@codspeed.io if the issue persists.