base32/base64/basenc: accept a -w value starting with - to match GNU

[AlejandroCoronadoN]

base64 -w -5 (and any -w value that starts with -, e.g. -w -d) was rejected by the argument parser with unexpected argument '-5' found, while GNU takes the token after -w as the wrap size and reports invalid wrap size:

$ printf abc | base64 -w -5
error: unexpected argument '-5' found
$ printf abc | gbase64 -w -5
gbase64: invalid wrap size: '-5'

Adding allow_hyphen_values(true) to the -w/--wrap argument lets the value reach the existing wrap-size parser, which already emits the GNU-matching message. Verified against GNU for -w -5, -w -d, -w -x (all invalid wrap size), with valid values (-w 5, -w0, --wrap=5) and decoding unchanged. The shared base_common.rs covers base32, base64 and basenc.

[codspeed-hq]

Merging this PR will not alter performance

✅ 178 untouched benchmarks
⏩ 229 skipped benchmarks¹

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_{Comparing AlejandroCoronadoN:base-wrap-hyphen-value (78daa23) 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. ↩

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/date/resolution (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!

[oech3]

Suggested change

// GNU takes the token after -w as the wrap size even when it starts with '-'.

Comment is unnecessary if you added test.