fix: use diff line index as 1-based line numbers

[2bndy5]

After doing some experiments, I found that the gix_imara_diff::Diff API uses 0-based line indexes instead of 1-based line numbers. Furthermore the gix_imara_diff::UnifiedDiff API uses 1-based line numbers when printing hunk headers (@@ -3,5 +3,6 @@). Thus, printing the unified diff into a patch file remains the same as it was already accurate.

So this patch increments the line indexes by 1 when they are be compared/normalized to ranges of 1-based line numbers.

I left the print_diff() function in the test module as a helper/proof when analyzing future regressions.

Summary by CodeRabbit

• Bug Fixes
  • Improved how changed lines are detected and reported, especially for additions, removals, and mixed diffs.
  • Fixed line numbers shown in removal suggestions so they now match what users see in the file.
  • Better handles ranges when a removal covers an existing selected range, reducing missed or duplicated suggestions.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI (base), Organization UI (inherited)

Review profile: CHILL

Plan: Pro

Run ID: c1632731-9231-4ee2-8680-310e5baa1b6d

📥 Commits

Reviewing files that changed from the base of the PR and between 29f82f6 and f20e7c7.

📒 Files selected for processing (1)

• cpp-linter/src/clang_tools/clang_format.rs

📝 Walkthrough

Walkthrough

The PR updates diff-to-line-range conversion to use 1-based inclusive bounds, adjusts overlap and pure-removal handling to match, and changes test and debug output to reflect the updated line numbering.

Changes

Diff range handling and output

Layer / File(s)	Summary
Clang-format range conversion cpp-linter/src/clang_tools/clang_format.rs	run_clang_format and three_way_diff convert diff hunks to 1-based inclusive ranges and change overlap and pure-removal handling to use the recalculated boundaries.
Clang-format tests and diff tracing cpp-linter/src/clang_tools/clang_format.rs	The clang_format tests switch to make_patch, update expected ranges, and add a feature-gated print_diff helper that renders unified diff lines with ANSI styling.
File hunk matching and suggestions cpp-linter/src/common_fs.rs	FileObj::is_hunk_in_diff and get_suggestions use 1-based inclusive line numbers, append_patch adjusts the patch header formatting call, and a pure-removal unit test checks the new suggestion text.
Colored patch output cpp-linter/tests/comments.rs	The comments test harness prints patch content line by line and colors added and removed lines with ANSI styling.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• cpp-linter/cpp-linter-rs#77: Shares the FileObj diff-range and suggestion-generation paths that this PR updates.
• cpp-linter/cpp-linter-rs#101: Also changes run_clang_format range conversion from gix_imara_diff data into line-based advice ranges.
• cpp-linter/cpp-linter-rs#358: Also updates three_way_diff range-merging and its tests in cpp-linter/src/clang_tools/clang_format.rs.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: converting diff line indexes to 1-based line numbers.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.38%. Comparing base (4958912) to head (f20e7c7).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #389      +/-   ##
==========================================
+ Coverage   92.26%   92.38%   +0.12%     
==========================================
  Files          23       23              
  Lines        3750     3796      +46     
==========================================
+ Hits         3460     3507      +47     
+ Misses        290      289       -1     

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