extract, list: auto-detect and decompress gzip archives

[kevinburke]

Previously, extract and list passed the raw file bytes directly to the tar parser without decompression. When given a .tar.gz file, the compressed gzip stream was interpreted as tar headers, producing errors like "numeric field did not have utf-8 text" on the checksum field.

Detect gzip compression by reading the two-byte magic number (0x1f 0x8b) at the start of the file, and wrap the reader in a GzDecoder when present. Plain .tar files continue to work as before.

Confirmed this patch allows extraction of Go source code from https://go.dev/dl/ (previously we would get an error).

[codecov]

Codecov Report

❌ Patch coverage is 99.43820% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.77%. Comparing base (791ae26) to head (f8884ba).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/uu/tar/src/compression.rs	98.62%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #168      +/-   ##
==========================================
+ Coverage   96.84%   97.77%   +0.92%     
==========================================
  Files          11       15       +4     
  Lines        1492     1751     +259     
  Branches       29       34       +5     
==========================================
+ Hits         1445     1712     +267     
+ Misses         46       38       -8     
  Partials        1        1              

Flag	Coverage Δ
macos_latest	97.77% <99.43%> (+0.92%)	⬆️
ubuntu_latest	97.77% <99.43%> (+0.92%)	⬆️
windows_latest	0.00% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[kaladron]

Hi Kevin! I'm holding this for just a bit while I get the support for reading from stdin in as that will change some function interfaces. I'll review this right after.

[kaladron]

Please tage #158 in the commit description.

[kevinburke]

I see quite a lot of patches just came in; anything I can help review?

[kaladron]

I see quite a lot of patches just came in; anything I can help review?

I filed Issues for each piece of missing functionality so that we can coordinate. If more people are showing up, I want them to be able to claim an issue rather than have any conflict. But I'll tag you in two others (that are blocking these at the moment)

[codspeed-hq]

Merging this PR will not alter performance

✅ 7 untouched benchmarks

---

_{Comparing kevinburke:kb-gzip-support (f8884ba) with main (9dd7012)}