Creates Pkg for external consumption

[amenocal]

This pull request refactors the project to move the core archive and commit remapping logic from the internal/ directory to a new public pkg/ package, making it available for use as a Go library. It also updates the CLI and documentation to reflect these changes, and improves the archive handling implementation for better security and compatibility. The most important changes are grouped below:

Library Extraction and Refactoring

• Moved archive extraction and packaging logic from internal/archive to pkg/archive, rewriting it for improved safety, error handling, and standards compliance. This includes a new UnTar and ReTarDir implementation, with legacy ReTar preserved for backward compatibility. ([pkg/archive/archive.goR1-R277](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-d73d8d6eb025db679b02c1d5e3209270958f4dbf182e6d05a6646970921d8542R1-R277))
• Moved commit remapping logic from internal/commitremap to pkg/commitremap, making the parsing and processing functions accessible for library consumers. ([cmd/root.goL11-R12](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-ab967ab1a2f3a1b769106eeb7bfe892ef0e81d1d27811fa15be08e6749feee1fL11-R12))
• Removed the now-obsolete internal/archive and internal/commitremap code and their tests. ([[1]](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-944e4f913612b11592545c5323f8b0542d04a0599177f29de14e03a3d93e25baL1-L85), [[2]](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-dffb7bab06af83e76768dcafc44e1f9b291acf0b33fd280dc65b970a0bba6ed2L1-L111), [[3]](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-9aee514456c5e2d82e4fa7a48ccf1610b747877bbae78cec79c39e358f149c33L1-L129), [[4]](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-908f3b040eead50105c334bd5112da44bf75b150350af4b059e01199666a4fedL1-L86))

CLI and Workflow Updates

• Updated the CLI (cmd/root.go) to use the new pkg/archive and pkg/commitremap packages, and switched to using commitremap.DefaultPrefixes() for file prefix selection. ([[1]](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-ab967ab1a2f3a1b769106eeb7bfe892ef0e81d1d27811fa15be08e6749feee1fL11-R12), [[2]](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-ab967ab1a2f3a1b769106eeb7bfe892ef0e81d1d27811fa15be08e6749feee1fL37-L39), [[3]](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-ab967ab1a2f3a1b769106eeb7bfe892ef0e81d1d27811fa15be08e6749feee1fL56-R53))
• Updated the GitHub Actions workflow to use go-version-file: go.mod for Go version management, ensuring consistency with the project's go.mod. ([.github/workflows/build.ymlL26-R26](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721L26-R26))

Documentation and Go Version

• Added a new section to the README.md describing how to use the remapping and archive logic as a Go library, including sample code and known limitations. ([README.mdR42-R93](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5R42-R93))
• Updated the Go version in go.mod from 1.21 to 1.24 to match current standards. ([go.modL3-R3](https://github.com/mona-actions/gh-commit-remap/pull/14/files#diff-33ef32bf6c23acb95f5902d7097b7a1d5128ca061167ec0716715b0b9eeaa5f6L3-R3))

[Copilot]

Pull request overview

This PR extracts the core archive and commit-remapping logic from internal/ into public pkg/ packages so the project can be consumed as a Go library, while updating the CLI/docs and hardening the tar handling.

Changes:

• Introduces pkg/archive with new UnTar/ReTarDir implementations and keeps ReTar for legacy CLI behavior.
• Introduces pkg/commitremap with public commit-map parsing and metadata rewrite helpers + expanded tests.
• Updates CLI, README, workflow, and Go version; removes the obsolete internal/* implementations/tests.

Show a summary per file

File	Description
pkg/commitremap/commitremap.go	New public commit map parsing + JSON SHA rewriting logic
pkg/commitremap/commitremap_test.go	New/expanded tests for parsing, prefix defaults, and rewriting behavior
pkg/archive/archive.go	New public tar extraction/creation implementation (security + compatibility oriented)
pkg/archive/archive_test.go	Extensive tests for tar safety, edge cases, and legacy layout parity
cmd/root.go	Switches CLI imports to pkg/* and uses DefaultPrefixes()
README.md	Adds “Using as a library” section and documents limitations
.github/workflows/build.yml	Uses go-version-file: go.mod for Go version selection
go.mod	Bumps declared Go version to 1.24
internal/archive/archive.go	Removed (superseded by pkg/archive)
internal/archive/archive_test.go	Removed (superseded by pkg/archive tests)
internal/commitremap/commitremap.go	Removed (superseded by pkg/commitremap)
internal/commitremap/commitremap_test.go	Removed (superseded by pkg/commitremap tests)

Copilot's findings

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• Files reviewed: 13/13 changed files
• Comments generated: 4