Use JGit to filter newly added/modified sql queries only for codegen

[swanandvk]

Feature: Add support for generating code for newly added or modified files based on git index.

Existing implementation:

It takes all the sql files provided in the configured directory for code generation.

New Implementation:

• If no GIT repository is configured in target project then fallback to default behaviour viz. use all sql files for codegen
• If any untracked file or modified file is available then use only those files for code generation

Advantage:

It does not depend on gradle cache hence the initial run also does not generate code for unintended files.