fix: make generated gitignore configurable

[sxlijin]

Summary

• add a gitignore = false generator setting while preserving the current default
• safely remove the writer-owned catch-all when the setting is disabled and preserve custom .gitignore files on subsequent generation
• document the setting for committed Rust SDK crates

Root cause

The shared SDK output writer always installed a catch-all .gitignore, so a normal git add of a generated crate silently staged only that file.

Validation

• cargo fmt --all -- --config imports_granularity="Crate" --config group_imports="StdExternalCrate"
• cargo clippy -p baml_cli --all-targets --all-features -- -D warnings
• cargo test -p baml_codegen_types --lib
• cargo test -p baml_cli --lib generator_gitignore
• cargo test -p baml_cli generate_rust_can_disable_generated_gitignore --test exit_code_e2e
• cargo test -p sdkgen_csharp --lib
• GitHub Actions: all 53 executed checks pass across Linux, Windows, macOS, musl, wasm, SDK, snapshot, documentation, MSRV, pre-commit, and size gates

Fixes #4373

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 08d3b1e8-b52b-4930-bce3-4e0638307a12

📥 Commits

Reviewing files that changed from the base of the PR and between 0f130a2 and 0e62c85.

📒 Files selected for processing (7)

• baml_language/crates/baml_cli/src/generate.rs
• baml_language/crates/baml_cli/src/manifest.rs
• baml_language/crates/baml_cli/tests/exit_code_e2e.rs
• baml_language/crates/baml_codegen_types/src/generator_fields.rs
• baml_language/crates/baml_codegen_types/src/output_writer.rs
• baml_language/sdks/csharp/sdkgen_csharp/src/lib.rs
• baml_language/sdks/rust/bridge_rust/README.md

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📝 Walkthrough

Walkthrough

The generator configuration now supports gitignore = false. The setting defaults to true, reaches C# and other output writers, persists in manifests when disabled, and preserves user-managed .gitignore files. Tests and Rust SDK documentation cover the behavior.

Changes

Generated output writer

Layer / File(s)	Summary
Writer policy and defaults baml_language/crates/baml_codegen_types/src/generator_fields.rs, baml_language/crates/baml_codegen_types/src/output_writer.rs	OutputWriterOptions controls generated .gitignore creation. The default remains enabled. Disabled generation preserves a user-managed root .gitignore.
Manifest parsing and CLI propagation baml_language/crates/baml_cli/src/manifest.rs, baml_language/crates/baml_cli/src/generate.rs	The CLI reads the optional gitignore setting, defaults it to true, serializes explicit false, and passes the policy to output writers.
SDK integration and validation baml_language/sdks/csharp/sdkgen_csharp/src/lib.rs, baml_language/crates/baml_cli/tests/exit_code_e2e.rs, baml_language/sdks/rust/bridge_rust/README.md	C# exposes generate_into_with_options. Rust end-to-end coverage verifies that disabled generation omits .gitignore. The README documents the configuration.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 0e62c

The change makes the generated .gitignore optional while preserving the current default behavior and supporting custom files on later generation; no actionable merge-blocking risk remains after normal checks.

Sequence Diagram(s)

sequenceDiagram
  participant Manifest
  participant CLI
  participant Generator
  participant OutputWriter
  participant Filesystem
  Manifest->>CLI: provide gitignore setting
  CLI->>Generator: store gitignore policy
  Generator->>OutputWriter: write generated output with options
  OutputWriter->>Filesystem: create or preserve .gitignore

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Suggested reviewers: hellovai, 2kai2kai2

Poem

A rabbit sets the switch just right,
The crate can show its files in sight.
A hidden star may stay away,
While user files remain each day.
Config and tests now hop in line.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The PR implements the requested gitignore = false option, preserves the default, and documents committed generated Rust crates [#4373].
Out of Scope Changes check	✅ Passed	The implementation, tests, API propagation, manifest support, and Rust documentation all directly support the linked issue.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: configurable generated .gitignore behavior.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch sxlijin/gh-4373-sdkgen-rust-generated-gitignore-makes-git

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[github-actions]

⏭️ Performance benchmarks were skipped

Perf benchmarks (CodSpeed) are opt-in on pull requests — they no longer run on every push. They always run automatically after merge to canary/main.

To run them on this PR, do any of the following, then push a commit (or re-run CI):

• Add RUN_CODSPEED=1 to the PR description, or
• Include run-perf or /perf in the PR title or any commit message.

[github-actions]

Binary size checks passed

✅ 7 passed

	Artifact	Platform	File	Gzip	Gated on	Baseline	Delta	Status
✅	baml-cli	Linux	🔒 31.8 MB	12.6 MB	file	31.7 MB	+99.9 KB (+0.3%)	OK
✅	packed-program	Linux	🔒 25.0 MB	9.2 MB	file	24.9 MB	+104.2 KB (+0.4%)	OK
✅	baml-cli	macOS	🔒 25.5 MB	11.1 MB	file	25.5 MB	+32.3 KB (+0.1%)	OK
✅	packed-program	macOS	🔒 20.6 MB	8.2 MB	file	20.6 MB	+91.4 KB (+0.4%)	OK
✅	baml-cli	Windows	🔒 27.3 MB	11.3 MB	file	27.2 MB	+105.4 KB (+0.4%)	OK
✅	packed-program	Windows	🔒 21.8 MB	8.3 MB	file	21.7 MB	+90.7 KB (+0.4%)	OK
✅	bridge_wasm	WASM	21.3 MB	🔒 5.4 MB	gzip	5.3 MB	+49.1 KB (+0.9%)	OK

🔒 = the size this artifact is GATED on (ceiling + delta). Binaries gate on file size (installed binary); WASM gates on gzip (download size). The other size is shown for information only.

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[sxlijin]

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