Fix baseline version selection for new releases

[Copilot]

Pull Request

Description

When generating build notes for a version not yet in history (e.g., 1.2.0 with existing releases 1.1.0 and 1.0.0), BuildMark incorrectly selected 1.0.0 as the baseline instead of 1.1.0.

Root Cause: DetermineSearchStartIndex in GitHubRepoConnector returned index 1 when the target version was not found in release history, skipping the most recent release at index 0.

Fix: Changed return value from 1 to 0 when toIndex == -1, ensuring search starts from the most recent release. GitHub orders releases newest-first, so index 0 is always the correct starting point for a new version.

// Before: Skipped most recent release
if (toIndex == -1 && releaseCount > 1)
    return 1;

// After: Start from most recent release  
if (toIndex == -1 && releaseCount > 0)
    return 0;

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
• Code quality improvement

Related Issues

Pre-Submission Checklist

Before submitting this pull request, ensure you have completed the following:

Build and Test

• Code builds successfully: dotnet build --configuration Release
• All tests pass: dotnet test --configuration Release
• Code produces zero warnings

Code Quality

• Code formatting is correct: dotnet format --verify-no-changes
• New code has appropriate XML documentation comments
• Static analyzer warnings have been addressed

Quality Checks

Please run the following checks before submitting:

• Spell checker passes: cspell "**/*.{md,cs}"
• Markdown linter passes: markdownlint "**/*.md"
• YAML linter passes: yamllint '**/*.{yml,yaml}'

Testing

• Added unit tests for new functionality
• Updated existing tests if behavior changed
• All tests follow the AAA (Arrange, Act, Assert) pattern
• Test coverage is maintained or improved

Documentation

• Updated README.md (if applicable)
• Updated ARCHITECTURE.md (if applicable)
• Added code examples for new features (if applicable)
• Updated requirements.yaml (if applicable)

Additional Notes

All 84 existing tests pass. CodeQL security scan shows no vulnerabilities. The fix is a single-line change with updated comments for clarity.

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Original prompt

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This section details on the original issue you should resolve

<issue_title>[Bug]: Target Version Selection</issue_title>
<issue_description>### Description

The wrong version is sometimes selected.

Steps to Reproduce

1. Have a repository with existing releases [1.0.0 and 1.1.0] and then some commits
2. Run BuildMark with a new version [1.2.0]
3. BuildMark picks 1.0.0 rather than 1.1.0 as the base version

Expected Behavior

BuildMark should pick 1.1.0 as the base and 1.2.0 as the new version - then include the commits done after 1.1.0 as the changes.

Actual Behavior

1.0.0 is selected rather than 1.1.0

Code Sample

Tool Version

Head build

.NET Version

.NET 8

Operating System

No response

Additional Context

The issue appears to be in DetermineSearchStartIndex where it returns 1 as the index ignoring the newest version in index 0. This decision should be reviewed - should it always be 0 or is there a reason why 1 would ever be the correct index.

Checklist

• I have searched existing issues to ensure this is not a duplicate
• I have provided a clear description of the problem
• I have included steps to reproduce the issue</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Bug]: Target Version Selection #39

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