Refactor: Enhance Git and Changelog Operations Robustness

[thomas-vilte]

Description

This pull request refactors and enhances the robustness of Git operations and changelog management within the release service. The primary goal is to make these critical processes more reliable, provide better debugging information through improved logging, and handle edge cases more gracefully.

Specifically, I improved the detection of staged changes, ensured Git commands are executed from the correct repository root, added checks for file existence before staging, and refined the logic for managing the CHANGELOG.md file, including handling empty "Unreleased" sections and consolidating link definitions. The parsing of version sections in the changelog has also been made more robust using regular expressions.

Fixes # (issue)

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

The changes primarily involve internal logic and Git command execution.

• Unit tests
• Integration tests
• Manual test: I manually verified the behavior of git add, git commit, HasStagedChanges, and changelog updates in various scenarios (e.g., with and without staged changes, with empty unreleased sections, with different versioning patterns).

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

🧪 Test Plan & Evidence

Suggested Manual Verification

• API/Backend: Attach JSON response or logs as evidence of correct behavior
• Performance: Ensure no significant latency increase
• Unit Tests: Run go test ./... and ensure all tests pass
• No Regressions: Verify that related features still work as expected