Add Git Sparse Checkout to Git Dag Bundle

[jscheffl]

Git Dag Budle does currently always a full clone of the Git repo. Not good in cases when you run Airflow on a big monorepo.

This PR adds support for Git Sparse Checkout.

I experimented a bit around, initial clone is still large as if first bare close in made with --filter=blob:none which would be optimal, then the local clones of the bare are not able to resolve the object SHAs and miss reference. Due to structure with clone from bare clone I have no idea to slim initial clone down. Might be future improvement for a Git expert. Or strategy with clone from bare clone need to be revised.

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[Copilot]

Pull request overview

Adds optional Git sparse-checkout support to GitDagBundle so monorepo users can materialize only selected directories in the working tree (cone mode). When sparse_dirs is provided, the local clone from the bare repo is performed with --sparse --no-checkout, followed by git sparse-checkout init --cone / set <dirs> and a checkout of the tracking ref. The initial bare clone is still full; the PR description acknowledges this as a future improvement.

Changes:

• New sparse_dirs: list[str] | None kwarg on GitDagBundle, threaded into log context and the clone logic.
• _clone_repo_if_required now conditionally adds --sparse --no-checkout clone options and configures cone-mode sparse checkout.
• Docs example updated to mention sparse_dirs; new unit test verifying that only files under the configured sparse dir are present.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
providers/git/src/airflow/providers/git/bundles/git.py	Adds sparse_dirs parameter and sparse-checkout setup after cloning from the bare repo.
providers/git/docs/bundles/index.rst	Documents the new sparse_dirs kwarg in the JSON config example.
providers/git/tests/unit/git/bundles/test_git.py	Adds test_sparse_checkout and type annotations to the git_repo fixture.