Add compression magic number detection to System.Formats.Tar with helpful error messages

[iremyux]

This PR improves error messages when users attempt to read compressed TAR archives. When TAR header parsing fails due to an invalid checksum field, the code now checks if the file might be a compressed archive (GZIP, BZIP2, XZ, ZIP, ZLIB, 7-Zip, or Zstandard) by examining compression magic numbers. If a compression format is detected, it throws a clear, localized error message indicating the specific compression format detected (e.g., "The file appears to be a GZIP archive. TAR format expected.").

Fixes #89056

[Copilot]

Pull Request Overview

This PR enhances the System.Formats.Tar library by adding compression format detection at the beginning of tar archive reading. When users attempt to read a compressed tar file directly without decompression, the library now provides helpful error messages that identify the compression type and guide users on the appropriate solution.

• Adds magic number detection for common compression formats (GZIP, ZLIB, BZIP2, LZ4, XZ, etc.)
• Provides differentiated error messages for supported vs unsupported compression formats
• Integrates compression checking into both synchronous and asynchronous tar reading workflows

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
TarHeader.Read.cs	Adds compression detection logic and calls to check magic numbers during tar header reading
Strings.resx	Adds localized error message templates for supported and unsupported compression detection

[Copilot]

Pull Request Overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

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[Copilot]

Pull Request Overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

[Copilot]

Pull Request Overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHeader.Read.cs:1

• The new ThrowIfCompressedArchive method lacks test coverage. Consider adding tests for each supported compression format (GZIP, BZIP2, XZ, Zstandard, ZIP, 7-Zip, ZLIB) to verify the detection logic and error messages work correctly. Tests should verify that each compression format's magic number is properly detected and throws the expected InvalidDataException with the correct format name.

// Licensed to the .NET Foundation under one or more agreements.

[Copilot]

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Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[rzikm]

LGTM