#261 feat(config): allow custom prompt template file via config

Summary

Add a templatePath config option that loads a custom prompt template file from disk, enabling users to define highly customized commit-message guidance without forking the project.

Changes

• feat: Add templatePath field to Config interface and COMMIT_ECHO_TEMPLATE_PATH env var override
• feat: Load template files with --- separator for system/user prompt splitting
• feat: templatePath takes precedence over inline systemPromptTemplate/userPromptTemplate
• feat: Init wizard prompts for template file path with existence validation
• test: Add 8 new tests for file loading, separator parsing, env var, missing file errors, and precedence

Template File Format

The template file supports the same {{variable}} syntax as inline templates:

• {{diff}} — The git diff text
• {{profile}} — The learned style profile summary
• {{branch}} — Current git branch name
• {{message}} — Previous commit message context

Use --- on its own line to separate the system prompt (above) from the user prompt (below). Without a separator, the entire file is used as the system prompt.

Example

You are an expert Git commit message assistant for the {{branch}} branch.

Style guidance:
{{profile}}

---
Generate 3 commit messages for:
```diff
{{diff}}

Testing

All 340 tests pass (including 8 new template file tests). Run with npm test.

Related

Closes #237

Summary by CodeRabbit

• New Features

  • Added support for custom prompt templates loaded from a file.
  • Templates can define separate system and user prompts using an optional separator.
  • Added configuration through an environment variable or configuration file.
  • The setup flow now validates template paths and reports the selected template.

• Bug Fixes

  • Improved prompt resolution in suggestions and dry-run output.
  • Added clearer errors when prompt template files cannot be read.

• Tests

  • Expanded coverage for template loading, configuration overrides, fallbacks, and validation.