Summary

This PR adds SSH commit signing functionality to Coder, enabling users to sign Git commits using their Coder SSH keys as an alternative to GPG signing. This builds on the existing Git SSH authentication system to provide a seamless signing experience.

Changes

New CLI Command

• coder gitsign: Hidden command that retrieves SSH keys from the agent and signs commit messages usingssh-keygen -Y sign
• Follows the same authentication patterns as the existinggitssh command
• Implements secure temporary key file handling with automatic cleanup
• Supports standard SSH signing protocol for Git commits

Agent Environment Configuration

• Modified agent to setGIT_CONFIG_GLOBAL environment variable
• Configures Git to use SSH signing instead of GPG:
  • gpg.format=ssh - enables SSH signing mode
  • gpg.ssh.program=coder gitsign - points to our signing command
  • commit.gpgsign=false - prevents automatic signing (user controlled)

Test Coverage

• Integration tests:TestGitSign with basic operation and key retrieval verification
• Agent tests:TestAgent_GitConfig validates environment variable setup
• All tests pass successfully and follow existing test patterns

How It Works

1. Setup: Agent configures Git environment to use SSH signing viaGIT_CONFIG_GLOBAL
2. Signing: When Git needs to sign a commit, it callscoder gitsign
3. Authentication: Command authenticates with Coder agent and retrieves user's SSH key
4. Execution: Usesssh-keygen -Y sign to sign the commit message
5. Cleanup: Temporary key files are securely removed

Usage

Users automatically get SSH commit signing enabled in Coder workspaces. Git will use their Coder SSH key to sign commits when configured to do so, providing an alternative to GPG signing without additional setup.

Testing

# Unit tests passgotest ./cli -run TestGitSigngotest ./agent -run TestAgent_GitConfig# Manual verificationcoder gitsign --help# Shows command help

Related

• Extends existing Git SSH authentication functionality
• Uses same SSH key management asgitssh command
• No breaking changes to existing functionality

AI Contribution Notice: This implementation was developed with AI assistance following Coder'sAI Contribution Guidelines. All code has been reviewed for correctness, security, and alignment with existing patterns.