Generated-file filtering uses user-supplied globs

Context

Users repeatedly ask to keep machine-generated sources - Qt moc_*.cpp, protobuf *.pb.cc, and the output of other code generators - out of compile_commands.json, so that clang-tidy and editor tooling run only over hand-written code. Two shapes were considered:

1. Bear ships built-in knowledge of common generator outputs and filters them automatically. This is wrong the day a project uses a generator Bear has never heard of, and it silently drops files a user may want kept.
2. The user supplies filename patterns in configuration, mirroring the existing directory-rule mechanism.

Glob matching needs a dependency. The candidates were glob (rust-lang owned, no transitive dependencies) and globset (faster, but pulls in regex-automata and its dependencies). Bear's source filtering runs once per entry over a set that is small relative to a whole build; matching speed is not a bottleneck.

Decision

User-supplied glob rules, evaluated with the same last-match-wins semantics as the directory rules. Use the glob crate for its zero-transitive-dependency footprint. Split basename-vs-full-path matching on whether the pattern contains a path separator, following the gitignore convention so that users' intuition carries over.

Consequences

There is no out-of-the-box filtering: a user writes two lines of configuration to exclude a generator's output. The man page carries the moc/protobuf recipes so the common cases are copy-paste. Directory rules and file-pattern rules compose (both must accept an entry), so the two mechanisms mix without surprising interactions. Revisit the globset choice only if profiling ever shows glob matching to be a real cost.

References

• Requirement: output-generated-file-filter
• Related: source-filter-last-match-wins