feat: add --batch-size flag to push refs in batches

[philip-gai]

Summary

This PR adds a --batch-size flag to the push and sync commands that allows pushing refs in smaller batches instead of all at once. This helps avoid server-side limits when syncing large repositories with many branches and tags.

Problem

When syncing repositories with a large number of refs (branches + tags), the push operation can fail due to server-side limits on the number of refs that can be pushed in a single operation.

Solution

• Add --batch-size flag (default: 0, meaning no batching for backward compatibility)
• When batch size is specified (minimum 10), collect all branch and tag refs and push them in batches
• Each batch creates explicit refspecs like +refs/heads/main:refs/heads/main instead of wildcards
• Gracefully handles "already up to date" responses per batch

Changes

• src/git.go: Add References() method to GitRepository interface
• src/push.go:
  • Add --batch-size flag with validation (must be 0 or >= 10)
  • Add collectRefs() function to gather branch and tag refs
  • Add pushRefsInBatches() function to push refs in smaller batches
• src/git_test.go: Add tests for git interface mocks
• src/push_test.go: Add comprehensive tests for batch validation, ref collection, and batch pushing
• script/bootstrap: Pin tool dependencies to versions compatible with Go 1.21

Usage

# Default behavior (no batching)
actions-sync push --destination-url https://ghes.example.com --destination-token $TOKEN

# Push refs in batches of 100
actions-sync push --destination-url https://ghes.example.com --destination-token $TOKEN --batch-size 100

Testing

• All new unit tests pass
• Docker-based lint and test passes
• Tested e2e on a GHES instance

[Copilot]

Pull request overview

This PR adds a --batch-size flag to the push and sync commands to enable pushing Git refs in smaller batches, helping avoid server-side limits when syncing repositories with many branches and tags.

Changes:

• Added --batch-size flag with validation (0 for no batching, or minimum 10)
• Implemented batching logic to collect and push refs in configurable batch sizes
• Added comprehensive unit tests for the new functionality
• Pinned tool dependencies to specific versions for Go 1.21 compatibility

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/push.go	Added batch-size flag, validation, collectRefs() function, and pushRefsInBatches() function to handle batched pushing
src/push_test.go	Added comprehensive tests for batch size validation, ref collection, and batched pushing functionality with mock implementations
src/git.go	Extended GitRepository interface with References() method and added (unused) RefInfo struct
src/git_test.go	Added tests verifying mock implementations satisfy the GitRepository and GitRemote interfaces
script/bootstrap	Pinned tool dependencies from @master to specific versions (v0.16.0, v1.6.0) for Go 1.21 compatibility

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