unexpand: accept a blank as a tab-list separator like GNU

[AlejandroCoronadoN]

GNU unexpand accepts both a comma and a blank between tab stops in -t/--tabs, so unexpand -t '2 3' behaves like unexpand -t '2,3'. uutils only splits on a comma, so the space form is rejected:

$ printf '  a   b\n' | unexpand -t '2 3' -a
unexpand: tab size contains invalid character(s): ' 3'

uutils' own expand already accepts both separators via an is_space_or_comma helper; only unexpand was inconsistent. This splits the tab list on a space or a comma too, mirroring expand. Verified byte for byte against GNU unexpand in the C locale for '2 3', ' 2 3', '2 3', '2, 3' and '1 4 7'; invalid values like -t x still error as before.

[codspeed-hq]

Merging this PR will improve performance by 3.84%

⚠️ 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
✅ 356 untouched benchmarks
⏩ 50 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	du_wide_tree[(5000, 500)]	20.5 ms	19.8 ms	+3.84%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing AlejandroCoronadoN:unexpand-space-tab-separator (7c49a86) with main (ec8adb5)}

Footnotes

1. 50 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. ↩

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/cp/sparse-to-pipe. tests/cp/sparse-to-pipe is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.
Note: The gnu test tests/env/env-signal-handler was skipped on 'main' but is now failing.

[oech3]

Not a useful function. Please remove it and write code directly.

[AlejandroCoronadoN]

Good point, removed the helper and inlined it as s.split([' ', ',']). Thanks for the review!

[sylvestre]

GNU splits on blank, so a literal TAB is a valid separator too - s.split([' ', '\t', ',']). expand's is_space_or_comma has the same gap; worth fixing both here.

[AlejandroCoronadoN]

Good catch, added the tab so the split is now s.split([' ', '\t', ',']). Verified against GNU unexpand with a tab separator. Thanks!