chgrp: reject the :gid format for the group operand

[vatsanbalaji-ossagent]

Currently, chgrp accepts group operands like :1000, even though GNU coreutils rejects this format. This change separates the group operand parsing from --from parsing, so the :gid syntax remains supported for --from but is rejected as a group operand. A regression test is also added to verify the behavior.

Closes #12792

🤖 Generated with Claude Code

[sylvestre]

test_numeric_group_formats still expects :gid to work as the target group, which is why CI is red. please update it

[vatsanbalaji-ossagent]

Thanks for catching this! test_numeric_group_formats was still using :gid as the target group. I've updated that step to use a plain numeric GID, so it still tests numeric group handling. The new test_invalid_group_with_colon_prefix test separately checks that :gid is rejected as a group operand.

I missed this locally because the test is skipped on macOS due to cfg(not(target_vendor = "apple")).

[codspeed]

Merging this PR will degrade performance by 22.05%

⚠️ 120 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• du_all_wide_tree[(5000, 500)]
• sort_mixed_utf8_locale
• sort_reverse_utf8_locale
• sort_unique_utf8_locale
• cksum_raw_output
• sort_very_long_lines_utf8_locale
• cksum_crc
• cksum_default
• du_summarize_balanced_tree[(5, 4, 10)]
• factor_64bit_semiprime
• …and 110 more

ℹ️ 1 benchmark has no flame graph

The flamegraph could not be generated because too much time was spent in runtime internals, making the visualization not useful for performance analysis.

• sort_dictionary_order[500000]

⚠️ 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
❌ 2 regressed benchmarks
✅ 398 untouched benchmarks
⏩ 70 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	factor_three_39_bit_primes	321.7 ms	597 ms	-46.11%
❌	Simulation	factor_five_38_bit_primes	1.5 s	1.8 s	-15.51%
⚡ ⚠️	Simulation	du_all_wide_tree[(5000, 500)]	35.7 ms	34.3 ms	+4.02%

Tip

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

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_{Comparing vatsanbalaji-ossagent:chgrp-colon-group (2a0c5fc) with main (1747ba1)}

Footnotes

1. 70 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. ↩