[somewhatabstract]

Stacked on #2707. These are the two pieces of fast-glob's matching that get_files needs in Rust. Both were written by the clean-room agent and checked against the micromatch build fast-glob 3.3.3 uses, run as a black box.

• Brace expansion (expand_braces): src/*.{js,ts} becomes src/*.js and src/*.ts. It handles comma lists, nesting and escapes, and braces that don't form a group stay literal.
  • Comparison: across 140,000 random patterns, the expansions match micromatch's in number and order. The text differs only where micromatch removes escape backslashes; we keep them, because each result is still a glob pattern.
  • Ranges: {1..3} is deliberately not expanded and stays literal.
• Dotfile option (GlobOptions::dot): with dot: false, no wildcard (*, ?, a set, **) matches a . at the start of a name, but a literal . in the pattern does. gitignore keeps dot: true, so its behaviour doesn't change.
  • Agreement with micromatch on 160,000 random cases: 97.8%.
  • Differences a file walk can't hit: micromatch lets x/** match the folder x itself, skips a leading ./ in a pattern, and treats ., .. and empty names specially. The walker and pattern-splitting steps cover the cases that matter.
  • Differences recorded for 12.0.0: micromatch's *.* doesn't match a., and its [!a] doesn't act as a negated set.

__conformance__/fastglob-vectors.json records 172 cases with micromatch's answers, plus a rust reason for each deliberate difference. Tests check both features against it.

expand_braces has no caller yet, so it carries a test-only dead_code expectation. The next PR, which splits include patterns, calls it and removes the expectation.

Part of #2615.

Test plan

• With dot: true, the glob matcher and IgnoreFile still agree with git on the earlier 500,000 glob cases and 150,000 path decisions. The clean-room agent's own runs: 100,000 glob cases and 110,182 decisions.

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Latest commit: 3f070b3

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Bundle size has no change ✅

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (69cbdb4) to head (3f070b3).

Additional details and impacted files

@@                                  Coverage Diff                                   @@
##           claude/jolly-galileo-72zesp-glob-gitignore-modules     #2708     +/-   ##
======================================================================================
  Coverage                                              100.00%   100.00%             
======================================================================================
  Files                                                     112       126     +14     
  Lines                                                    3843      5085   +1242     
  Branches                                                 3051      4293   +1242     
======================================================================================
+ Hits                                                     3843      5085   +1242     

Flag	Coverage Δ
rust	100.00% <100.00%> (ø)
typescript	100.00% <ø> (ø)

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Files with missing lines	Coverage Δ
...ates/checksync-core/src/gitignore/relative_path.rs	100.00% <ø> (ø)
...tes/checksync-core/src/glob/advance_any_folders.rs	100.00% <100.00%> (ø)
.../checksync-core/src/glob/advance_glob_positions.rs	100.00% <100.00%> (ø)
...crates/checksync-core/src/glob/advance_one_byte.rs	100.00% <100.00%> (ø)
...ust/crates/checksync-core/src/glob/advance_star.rs	100.00% <100.00%> (ø)
...rates/checksync-core/src/glob/brace_bracket_end.rs	100.00% <100.00%> (ø)
...rates/checksync-core/src/glob/brace_results_fit.rs	100.00% <100.00%> (ø)
...es/checksync-core/src/glob/byte_matcher_matches.rs	100.00% <100.00%> (ø)
...c-core/src/glob/byte_matcher_matches_hidden_dot.rs	100.00% <100.00%> (ø)
...tes/checksync-core/src/glob/combine_brace_texts.rs	100.00% <100.00%> (ø)
... and 14 more

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[somewhatabstract]

Test (windows-latest) is failing on this PR, and the failure is this PR's. A deep-nesting brace expansion test overflows the stack on Windows debug builds (STATUS_STACK_OVERFLOW). Brace expansion recurses once per nesting level, and 64 levels of debug-sized frames don't fit in a Windows thread's stack. A fix is in progress: it replaces the recursion with a heap-allocated work stack, and adds a small-stack test so the problem also shows up on Linux.

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