Gitlab code quality report must use forward slash in paths

[mathieugouin]

Summary

(issue was originally discussed in #14732 )

If the gitlab report is ran on a windows host, the generated paths in the json file have backslashes (\).

However, gitlab does not accept backslashes in path for the report to work, they have to be forward slashes (/).

The command to reproduce the problem (must run on a windows host):

ruff check --exit-zero --no-cache --output-format gitlab --output-file python-gl-codequality.json

Version

ruff 0.12.11 (c2bc15bc1 2025-08-28)

[ntBre]

Thanks for the report! I can look into this since I've been working on the GitLab output format recently, unless someone beats me to it :)