November 2025 monthly summary for rust-lang/cargo focusing on packaging backup exclusions and test coverage. Key features delivered: - Implemented CACHEDIR.TAG handling in cargo packaging to exclude temporary artifacts from backups by creating CACHEDIR.TAG files in build directories during package generation (build/ directories) using create_dir_all_excluded_from_backups_atomic. - Augmented packaging tests to validate correct CACHEDIR.TAG placement: the tag exists in build directories and is not created in the final target directory. Major bugs fixed: - Fixed bug where cargo package did not create CACHEDIR.TAG in the target directory, leading to temporary packaging artifacts being included in backups; introduced and updated tests to reflect the corrected behavior. (Related to #16238). Overall impact and accomplishments: - Reduces backup noise and risk by ensuring temporary packaging artifacts are excluded from system backups (e.g., Time Machine on macOS), improving packaging reliability and developer experience during distribution. - Demonstrates end-to-end ownership of a packaging reliability improvement, including test-driven validation and cross-module integration. Technologies/skills demonstrated: - Rust, cargo packaging pipeline, filesystem operations (CACHEDIR.TAG creation), atomic directory operations, cross-platform backup exclusions, test-driven development, and issue-driven delivery (#16238).