[FIX]: Force LF line endings for helpdesk mitigation.patch on Windows

[Sumit Kumar (sumit1kr)]

Closes #12

test_patch fails on Windows because git apply converts LF to CRLF,
causing a byte-level mismatch in the patch round-trip test.

Adding helpdesk-bot/mitigation.patch text eol=lf to .gitattributes
forces Git to preserve LF on all platforms, fixing the test on Windows
without affecting any other files.

[Nina Chikanov (nina-msft)]

Hey Sumit Kumar (@sumit1kr) - sorry it took a while to get back to you! We are working on a better process to monitor both repos :-)

This PR title advertises a narrow fix, specifically for the tagged issue (#12) ...but the code changes ship an entirely new langgraph-rag-poisoning showcase plus the change.

If you would like to contribute the new example, please separate from this branch and open a new PR with a [FEAT] tag. Once that is done and this PR is refocused, feel free to tag me and I'll take another look.

Thanks!

[Copilot]

Pull request overview

This PR addresses a Windows-only test failure where mitigation.patch is checked out with CRLF (due to Git autocrlf), causing a byte-level mismatch in the patch round-trip test. It updates Git attributes so the patch’s line endings remain LF across platforms.

Changes:

• Updates .gitattributes to force LF line endings for helpdesk-bot/mitigation.patch.

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[Sumit Kumar (sumit1kr)]

Hi Nina Chikanov (@nina-msft) — done! The langgraph-rag-poisoning showcase has been moved to a separate PR: #15. This PR now only contains the .gitattributes fix for #12. Also addressed Copilot's review — restored the general *.patch -text -eol rule so only helpdesk-bot/mitigation.patch gets the LF override. Please re-review when ready!

[Nina Chikanov (nina-msft)]

Sumit Kumar (@sumit1kr) can you verify that this fix addresses the issue on Windows?

I asked GitHub Copilot to verify and it is asserting the error still stands:

assert post_reverse_bytes == original_bytes
E  At index 38 diff: b'\r' != b'\n'

Here is the provided rationale:

Here's why. The problem is in a different file (agent.py), not mitigation.patch. The test creates a brand-new temporary Git repo to do its work — and that temp repo does not have a .gitattributes file. So the .gitattributes line you added never gets used by the test.

Inside that temp repo, Git has a setting (core.autocrlf=true, which is normal on Windows) that quietly changes agent.py's line endings from LF to CRLF when it applies the patch. That change is what makes the test fail.

(A normal person cloning this repo won't hit this bug, because the real repo already forces LF. Only the empty temp repo in the test has the problem.)

How to fix it. The fix needs to go in the test file (tests/helpdesk/test_patch.py), not .gitattributes. Make the temp repo behave like the real one. I tested two ways that both work:

• Add a .gitattributes file (with * text=auto eol=lf) into the temp repo before the test runs its Git commands, or

• Turn off the line-ending setting in the temp repo: git("config", "core.autocrlf", "false")

⚠️ One warning: doing git -c core.autocrlf=false init does not work. That setting only lasts for that one command, and the test runs each Git command separately, so the patch step still uses the old setting. I tried it — it still fails.

Small note: the line you added is missing a newline at the end of the file. A local pre-commit run will complain about it (though CI won't, since CI doesn't run pre-commit).

[Sumit Kumar (sumit1kr)]

Hi Nina Chikanov (@nina-msft),

Thank you for catching that! You were completely right — the previous fix modifying .gitattributes only applied to the outer repository. The pytest execution builds and runs the patch check in a sandbox temporary repository (tmp_path / "demo") outside the project root, meaning it never read the .gitattributes rules and still fell back to the system/global core.autocrlf setting (which defaults to true on Windows).

To fix this properly, I went with Option B:- Added git("config", "core.autocrlf", "false") immediately after git init in the temp repo inside test_patch.py. This ensures no CRLF conversion occurs during the test runtime on Windows.

• Also verified .gitattributes terminates with a trailing newline.

Let me know if this looks good to go!

[Nina Chikanov (nina-msft)]

Thanks for fixing this!