docs: add origin note to README

[bschellenberger2600]

Adds a brief Origin section to the README explaining that git-testkit was extracted from git-fire before launch and published as a standalone library.

🤖 Generated with Claude Code

---

Note

Low Risk
Documentation-only changes (README badges/origin note and new package-level doc.go) with no impact on runtime behavior.

Overview
Adds README badges and a new Origin section describing git-testkit’s extraction from git-fire.

Introduces a package-level doc.go with GoDoc describing the main entry points (CreateTestRepo, NewScenario, SnapshotRepo/RestoreSnapshot) and a short quickstart example.

^{Reviewed by Cursor Bugbot for commit 544db1b. Bugbot is set up for automated code reviews on this repo. Configure here.}

Summary by CodeRabbit

• Documentation
  • Updated README: added status and reference badges and a new "Origin" section describing the project’s extraction and standalone release.
  • Added package-level documentation describing a test helper library for exercising real Git repositories, including primary helper entry points and guidance on using the helpers with the testing framework.

[coderabbitai]

📝 Walkthrough

Walkthrough

Added README badges and a new "Origin" section describing extraction of git-testkit from git-fire and publication as a standalone Go library. Added doc.go with package-level documentation for package testutil describing intended test helper entry points and usage patterns. No code or API signatures changed.

Changes

Cohort / File(s)	Summary
README updates README.md	Added CI, Go Reference, Go version, Latest Release, and MIT License badges; introduced a new "Origin" section describing extraction from git-fire and standalone publication.
Package documentation doc.go	New package doc for package testutil describing public surface area and helper entry points (CreateTestRepo, NewScenario, SnapshotRepo/RestoreSnapshot) and how helpers integrate with testing.T. No exported signatures introduced or changed.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 I hopped from fire to a tidy kit,
A README badge, an origin writ.
Doc lines whisper how tests should run,
Quiet helpers, crafted, one by one.
Hooray for tiny changes, neatly done! 🎉

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title 'docs: add origin note to README' accurately describes the main change—adding an Origin section to the README explaining git-testkit's extraction from git-fire. However, the changeset also includes badge additions and a new doc.go file, making the title partially incomplete.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch add-origin-note

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[bschellenberger2600]

bugbot review

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 544db1b. Configure here.}