Add optional fetch_depth option for shallow clones

[justinxu421]

Add configurable fetch depth support to optimize checkout performance in large repositories.

Key Changes

• New fetch_depth input parameter in action.yml with default value of '0' (full history) for backward compatibility
• Performance optimization documentation added to README.md explaining when and how to use shallow clones
• Updated example workflows with inline comments guiding users on choosing between shallow (fetch-depth: 1) and full clones (fetch-depth: 0)

Benefits

• Faster checkouts: Shallow clones significantly reduce checkout time for repositories with extensive history
• Flexible configuration: Users can specify '0' for full history, '1' for latest commit only, or any positive integer for specific depth
• Backward compatible: Default behavior unchanged, maintaining full history fetch

Usage Example

For most PR review scenarios:

- uses: actions/checkout@v4
  with:
    fetch-depth: 1  # Shallow clone for faster checkout

For workflows requiring more history:

- uses: actions/checkout@v4
  with:
    fetch-depth: 50  # Last 50 commits

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[github-actions]

The documentation updates are helpful, but there's a critical implementation issue: the fetch_depth input parameter is defined but never used by the action.

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[github-actions]

Critical Issue: Parameter defined but not passed to implementation

The fetch_depth input is defined here but is never passed to the action's implementation. Looking at lines 74-88, the environment variables section doesn't include INPUT_FETCH_DEPTH.

To fix this, you need to add the following to the env: block (around line 88):

INPUT_FETCH_DEPTH: ${{ inputs.fetch_depth }}

However, there's a deeper conceptual issue: this action doesn't perform any git checkout operations. The fetch-depth parameter is meant for actions/checkout@v4, which users already call in their workflows before this action runs. Adding fetch_depth as an input to this action serves no purpose since the checkout has already happened by the time this action executes.

Recommendation: Remove the fetch_depth input from action.yml entirely. The documentation updates showing users how to use fetch-depth with actions/checkout@v4 are valuable and should be kept, but this action doesn't need to accept or handle this parameter.

[github-actions]

Documentation Issue: Parameter doesn't belong to this action

This documents fetch_depth as an input to the Augment Agent action, but this parameter should not be part of this action's interface. The fetch-depth parameter belongs to actions/checkout@v4, not to this action.

The Performance Optimization section (lines 67-82) correctly shows users how to configure fetch-depth for actions/checkout@v4, which is the right approach. However, this line in the inputs table incorrectly suggests that fetch_depth is an input to the Augment Agent action itself.

Recommendation: Remove this row from the inputs table. The Performance Optimization section already provides clear guidance on using fetch-depth with the checkout action.