Feature: Add patch action to file_write tool

[Aaronontheweb]

Problem

Currently, file_write requires providing the full file content, which is cumbersome for surgical edits.

Proposed Solution

Add a patch action to file_write that supports:

• Action: "patch"
• Path: file to modify
• OldString: text to find
• NewString: replacement text
• ReplaceAll: boolean (optional, default false)

Benefits

• Cleaner for small edits without full file reads
• Safer (less chance of accidentally overwriting unrelated sections)
• Aligns with user workflow preferences

Implementation Notes

• Should support both single-replace and multi-replace modes
• Consider adding OldText / NewText as alternative parameter names for consistency with other tools

[Aaronontheweb]

File Write Tool Limitations

I attempted to implement issue #146 (replacing the hand-rolled FakeTimeProvider with Microsoft.Extensions.TimeProvider.Testing), but encountered significant limitations with the file_write tool.

Current Workarounds Required

To replace the FakeTimeProvider class across 5 test files, I needed to:

1. Add using statements: Used Python regex to insert using Microsoft.Extensions.TimeProvider.Testing; after the first using line in each file
2. Remove class definitions: Used Python regex to delete the entire private sealed class FakeTimeProvider block from each file
3. Verify changes: Checked each file to ensure no remnants remained

Tool Surface Gap

The current file_write tool requires providing the full file content to make surgical edits. This is problematic for:

• Adding/removing single lines (e.g., import statements)
• Replacing small code blocks without reading the entire file first
• Multi-file batch edits (requires 5+ round trips)

Recommended Tool Surface

A patch action would significantly improve developer experience:

// New file_write parameters:
{
  "Action": "patch",
  "Path": "src/Netclaw.Actors.Tests/Reminders/SetReminderToolTests.cs",
  "OldString": "    private sealed class FakeTimeProvider(DateTimeOffset utcNow) : TimeProvider\n    {\n        public override DateTimeOffset GetUtcNow() => utcNow;\n    }",
  "NewString": "", // or replacement text
  "ReplaceAll": false
}

Benefits:

• ✅ No need to read entire file before editing
• ✅ Safer for targeted modifications
• ✅ Cleaner for small changes (like removing 4 lines)
• ✅ Aligns with user workflow preferences

Next Steps

This workaround demonstrates the value of a patch action. Would be happy to help prototype this if useful!