feat: add fix-patch-path output variable

[2bndy5]

resolves #376

This is the result of

• feat: merge review suggestions from both clang tools #358
• feat: get clang-tidy fixes regardless of tidy-review value #354
• feat: use diff instead of clang-format XML output #347

If there are any auto-fixes available, then a patch full of them is created and its path is set to a new output fix-patch-path output variable.

If there were no auto-fixes, then the output variable is not set. Remember, an unset output variable is treated as an empty string (a false value) in steps.linter.outputs.fix-patch-path context.

Summary by CodeRabbit

Release Notes

• New Features

  • Auto-fix patches are aggregated into a single unified patch file in the repository cache directory.
  • CI/CD now receives an optional fix-patch-path output (with normalized forward slashes) pointing to the generated patch when present.
  • Cached patch aggregation is recorded consistently when producing suggestions.

• Bug Fixes

  • Clear any previously generated unified patch before starting a new run to prevent stale outputs.

• Tests

  • Updated test inputs to ignore build/** and added validation for the generated patch file contents.

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ℹ️ Review info

⚙️ Run configuration

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

Review profile: CHILL

Plan: Pro

Run ID: da445678-52e5-481a-b802-ee63fbf1ed19

📥 Commits

Reviewing files that changed from the base of the PR and between 006b65f and 5c0b165.

📒 Files selected for processing (7)

• cpp-linter/src/cli/structs.rs
• cpp-linter/src/common_fs.rs
• cpp-linter/src/error.rs
• cpp-linter/src/rest_client.rs
• cpp-linter/src/run.rs
• cpp-linter/tests/comments.rs
• cpp-linter/tests/reviews.rs

📝 Walkthrough

Walkthrough

Adds a ClangParams::AUTO_FIX_PATCH constant and three new FileObjError IO variants. Implements FileObj::maybe_append_patch and append_patch methods that compute and append a unified diff into .cpp-linter-cache/auto-fix.patch. Integrates these methods into post_feedback to call them for non-PR-review events and emit a fix-patch-path output variable. Cleans up old patch files before each run and updates test infrastructure to verify patch generation with glob pattern updates from build to build/**.

Changes

Auto-fix patch file generation and output

Layer / File(s)	Summary
AUTO_FIX_PATCH constant and FileObjError variants cpp-linter/src/cli/structs.rs, cpp-linter/src/error.rs	Defines the "auto-fix.patch" filename constant on ClangParams and adds MkDirFailed, OpenPatchFileFailed, and WritePatchFailed variants to FileObjError, each wrapping std::io::Error.
FileObj patch-writing methods cpp-linter/src/common_fs.rs	Adds std::io::Write and ClangParams imports. Implements maybe_append_patch(repo_root) (reads cached patched file and original, diffs them, normalizes path separators) and private append_patch (creates cache dir via CACHE_DIR, appends unified diff with zero context to AUTO_FIX_PATCH). Updates make_suggestions_from_patch to use to_string_lossy() and invoke append_patch before generating suggestions.
post_feedback integration and fix-patch-path output cpp-linter/src/rest_client.rs	Imports ClangParams. Extends post_feedback with a non-PR-review branch that calls file.maybe_append_patch(...) per file, then writes a fix-patch-path output variable pointing to the slash-normalized patch path when the file exists.
Initialization cleanup and test setup cpp-linter/src/run.rs	Deletes the auto-fix patch file from cache before run_main proceeds, ensuring fresh state. Updates test module to import ClangParams and modifies force_debug_output test to create the cache directory and write a dummy patch file for cleanup verification.
Test harness updates cpp-linter/tests/comments.rs, cpp-linter/tests/reviews.rs	Updates the ignore glob from -i=build to -i=build/** in both test setups. Adds fs import and post-run logic in comments.rs to locate the fix-patch-path= output line, assert the patch file exists, read its content, and print it.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• cpp-linter/cpp-linter-rs#354: Both PRs modify the same patch/suggestion flow in cpp-linter/src/common_fs.rs—make_suggestions_from_patch now records cached patches—so the main PR's auto-fix patch caching builds directly on fetched clang-tidy fixes behavior.
• cpp-linter/cpp-linter-rs#358: The main PR extends common_fs.rs's make_suggestions_from_patch and FileObj patch handling to append unified auto-fix patches to cache and expose fix-patch-path, building on the retrieved PR's refactor of FileObj/patch-driven suggestion generation for clang-tidy and clang-format merging.
• cpp-linter/cpp-linter-rs#377: Modifies RestClient::post_feedback control flow around the PR-review path, the same function this PR extends to call maybe_append_patch and emit the fix-patch-path output variable.

🚥 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 directly and clearly describes the main feature: adding a fix-patch-path output variable to expose auto-fix patches.
Linked Issues check	✅ Passed	The PR implements all coding objectives from issue #376: saves patch to .cpp-linter-cache/auto-fix.patch, sets fix-patch-path output variable, and integrates with prior auto-fix generation work.
Out of Scope Changes check	✅ Passed	All changes directly support the primary objective of exposing auto-fix patches via the fix-patch-path output variable; no unrelated code modifications detected.
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%.

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[2bndy5]

@shenxianpeng This is the preferred solution to compliment cpp-linter/cpp-linter-action#439

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.54%. Comparing base (fc75245) to head (5c0b165).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #378      +/-   ##
==========================================
+ Coverage   92.41%   92.54%   +0.12%     
==========================================
  Files          23       23              
  Lines        3637     3700      +63     
==========================================
+ Hits         3361     3424      +63     
  Misses        276      276              

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