fix(builtins): option gaps from gap telemetry (tar, gzip -c, grep -I/-r paths, join -o, xargs -r)

[chaliy]

Requested by Михайло · project thread

What changed

Closes the most common option gaps found by replaying 4,030 recorded agent calls (gap telemetry, #2552):

• tar: GNU long options (--strip-components, --exclude, --file, --directory, --create/--extract/--list, --to-stdout, no-op ownership flags), extract/list of named members ("Not found in archive", exit 2), unknown long option exits 2.
• gzip/gunzip: -c/--stdout, -1..-9/--fast/--best, binary-safe stdin/stdout.
• grep: -I / --binary-files=without-match|text|binary; grep -r prints GNU-style paths (d/b, ./b, bare b with no operand, no prefix for a single file operand) instead of absolute VFS paths; walks directories in name order.
• join: rewritten to GNU semantics (-o FORMAT/auto, -e, -v, -a, -j, -i, --header, cartesian product, check-order flags).
• xargs: empty input runs the command once (GNU default); -r/--no-run-if-empty skips it.

Why

These were top entries in the gap report: agents commonly run tar --strip-components=1, gzip -c, grep -rI, join -o and xargs -r, and failed or got wrong output.

Before

$ cd /tmp/g && grep -r needle .
/tmp/g/./a:needle
$ printf '' | xargs echo none
                      # (nothing; GNU prints "none")

xargs -r, gzip -c, grep -I, tar --strip-components/--exclude, and join -o were not supported.

After

$ cd /tmp/g && grep -r needle .
./a:needle
$ printf '' | xargs -r echo none
$ printf '' | xargs echo none
none
$ tar --strip-components=1 -xf t.tar   # extracts with first component stripped

New spec cases (tar, join, gzip, grep, xargs) pass against real bash/GNU tools and bashkit.

Risk

Low to medium. grep -r output paths changed from absolute to operand-relative (matches GNU; tests that grepped for absolute paths with an absolute operand are unaffected). xargs with empty input now runs the command once, as GNU does.

Checklist

• Failing spec cases first, then fixes
• cargo fmt, cargo clippy -D warnings
• Full bashkit lib + integration tests
• Knowledge log updated

https://claude.ai/code/session_019aFikmptPc91Fj4N2iDXQA

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Generated by Claude Code

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