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apply_patch

The apply_patch tool applies unified diff patches to multiple files in a single operation. It supports custom patch headers for adding, deleting, and updating files, making it ideal for complex multi-file refactoring operations.

Parameters​

The tool accepts these parameters:

  • patch (required): A unified diff patch string with custom headers. Supports *** Add File:, *** Delete File:, and *** Update File: headers.

What It Does​

This tool processes unified diff patches containing operations for multiple files. It parses the patch content, identifies file operations (add, delete, update), and applies the changes atomically. Unlike apply_diff which handles single-file search-and-replace operations, apply_patch works with traditional unified diff format.

When is it used?​

  • When applying patches generated by version control systems or diff tools
  • When performing complex multi-file refactoring with precise line-level changes
  • When migrating code changes from one branch or repository to another
  • When bulk-adding, updating, or removing multiple files in one operation
  • When working with patches from external sources or automated tools

Key Features​

  • Supports multiple files in a single patch operation
  • Handles file addition, deletion, and modification
  • Uses unified diff format for precise line-level control
  • Custom headers (*** Add File:, *** Delete File:, *** Update File:) for clarity
  • Atomic operations with validation before applying changes
  • Compatible with standard diff/patch tooling output

Limitations​

  • Requires proper unified diff format syntax
  • Line numbers and context must match existing file content
  • Cannot apply patches with conflicts or mismatched context
  • Less flexible than search-and-replace tools for fuzzy matching
  • Requires exact line-level accuracy in patches

How It Works​

When the apply_patch tool is invoked, it follows this process:

  1. Patch Parsing: Parses the patch string to identify custom headers (*** Add File:, *** Delete File:, *** Update File:) and unified diff blocks.
  2. Operation Identification: Groups changes by file path and operation type (add, delete, update).
  3. Validation: Validates that target files exist (for updates/deletes) or can be created (for adds).
  4. RooIgnore Check: Ensures target files are not restricted by .rooignore rules.
  5. User Review: Presents the patch operations for user review and approval.
  6. Application: Applies approved changes to each file sequentially.
  7. Feedback: Reports success or failure for each file operation.

Patch Format​

The patch format uses custom headers followed by unified diff blocks:

*** Add File: src/utils/newHelper.ts
--- /dev/null
+++ b/src/utils/newHelper.ts
@@ -0,0 +1,5 @@
+export function helperFunction(value: string): string {
+  return value.toUpperCase();
+}

*** Update File: src/main.ts
--- a/src/main.ts
+++ b/src/main.ts
@@ -10,7 +10,7 @@
 import { config } from './config';
-const timeout = 5000;
+const timeout = 10000;

 function main() {

*** Delete File: src/deprecated/oldUtil.ts

Relation to Other Tools​

  • apply_diff: Use for single-file search-and-replace with fuzzy matching
  • apply_patch: Use for multi-file operations with unified diff format
  • write_to_file: Use for creating entire new files