refactor: clean up some code

[DaniPopes]

Description

Some clean up opportunities I found while reading the code.

No functional changes intended.

Please let me know if breaking changes are a concern for you, I can revert the change to the public API in the core crate.

Motivation and Context

Refactor

How Has This Been Tested?

cargo test + cargo clippy

Screenshots / Logs (if applicable)

Types of Changes

• [ ] 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 change)
• [ ] Documentation (no code change)
• [x] Refactor (refactoring production code)
• [ ] Other

Checklist:

• [x] My code follows the code style of this project.
• [x] I have updated the documentation accordingly.
• [x] I have formatted the code with rustfmt.
• [x] I checked the lints with clippy.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[welcome[bot]]

Thanks for opening this pull request! Please check out our contributing guidelines! ⛰️

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 1.31579% with 75 lines in your changes missing coverage. Please review.

Project coverage is 37.04%. Comparing base (35b886e) to head (51f5b4d). Report is 195 commits behind head on main.

Files with missing lines	Patch %	Lines
git-cliff/src/lib.rs	0.00%	55 Missing :warning:
git-cliff-core/src/repo.rs	0.00%	18 Missing :warning:
git-cliff-core/src/changelog.rs	33.34%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #709      +/-   ##
==========================================
+ Coverage   36.66%   37.04%   +0.38%     
==========================================
  Files          20       20              
  Lines        1544     1531      -13     
==========================================
+ Hits          566      567       +1     
+ Misses        978      964      -14     

Flag	Coverage Δ
unit-tests	37.04% <1.32%> (+0.38%)	:arrow_up:

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[DaniPopes]

@orhun should be good now :pray:

[welcome[bot]]

Congrats on merging your first pull request! ⛰️

[orhun]

Awesome work, thanks a lot!