feat: allow specifying the base commit for local (non-CI) diffs

[2bndy5]

• ref feat: Allow specifying the base commit for local (non-CI) diffs cpp-linter#180
• as discussed in support explicitly choosing the ref commits to use for diffs cpp-linter#179

Summary by CodeRabbit

• New Features

  • Added --diff-base and --ignore-index CLI options to control base diffs and staged-file handling.

• Documentation

  • Documented new CLI options (minimum version 1.12.0).
  • Improved CLI argument header formatting to handle missing short names.

• Chores

  • Default test filter updated to exclude a specific test.

• Tests

  • Tests expanded to cover diff-base and ignore-index behaviors and updated call sites.

[coderabbitai]

Walkthrough

Adds diff_base and ignore_index CLI options, threads them through git diff resolution and REST API listing, makes git diff functions generic over printable refs, adjusts diff/staging logic, updates call sites and tests, and adds CLI/docs metadata; also adds a test exclusion to .config/nextest.toml.

Changes

Cohort / File(s)	Summary
CLI & Config cpp-linter/src/cli/mod.rs, docs/cli.yml, .config/nextest.toml	Introduced diff_base: Option<String> (-b/--diff-base) and ignore_index: bool (--ignore-index) in SourceOptions; added diff-base and ignore-index inputs to docs/cli.yml; extended test filter in .config/nextest.toml to exclude test(#repo_get_sha).
Git module cpp-linter/src/git.rs	Made get_sha generic over Display for flexible ref/depth input; added pub fn get_diff<'d, T: Display>(repo, diff_base: &Option<T>, ignore_index: bool) implementing staged vs tree diff selection and base resolution; updated parse_diff signature and accompanying tests/helpers.
REST API / GitHub cpp-linter/src/rest_api/mod.rs, cpp-linter/src/rest_api/github/mod.rs	Propagated generic T: Display and new params (diff_base, ignore_index) into get_list_of_changed_files; CI/REST and local git paths now call get_diff(..., diff_base, ignore_index) and parse accordingly; tests and mocks updated to new signature.
Integration & Call sites cpp-linter/src/run.rs, cpp-linter/tests/paginated_changed_files.rs	Updated call sites to pass &cli.source_options.diff_base and cli.source_options.ignore_index; tests updated to pass &None::<u8>, false where applicable.
Docs generation docs/src/lib.rs	Refactored argument header assembly to conditionally include short option when present, avoiding errors when short names are absent.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• fix: propagate errors #47 — modifies src/git.rs and diff handling; strongly related to get_diff/ref resolution changes.
• resort to paginated requests for changed files #37 — adjusts changed-files retrieval and get_list_of_changed_files behavior; related to REST API signature changes.

Suggested labels

documentation

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title clearly and specifically describes the main change: adding support for specifying the base commit for local diffs, which aligns with the changeset's primary objective.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch diff-base

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[codecov]

Codecov Report

❌ Patch coverage is 94.57364% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.90%. Comparing base (6002ba2) to head (eb3d529).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cpp-linter/src/git.rs	92.78%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #260      +/-   ##
==========================================
- Coverage   97.04%   96.90%   -0.14%     
==========================================
  Files          14       14              
  Lines        3078     3167      +89     
==========================================
+ Hits         2987     3069      +82     
- Misses         91       98       +7     

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[2bndy5]

@@            Coverage Diff             @@
##             main     #260      +/-   ##
==========================================
- Coverage   97.04%   96.90%   -0.14%     
==========================================
  Files          14       14              
  Lines        3078     3167      +89     
==========================================
+ Hits         2987     3069      +82     
- Misses         91       98       +7     

The 7 lines missing coverage are all related to providing better error messages. There's little benefit in adding tests that cover these lines.