Add additional CLI flags to configure `bun test --coverage`

[jack-weilage]

What is the problem this feature would solve?

Bun currently has an option to configure coverage thresholds in bunfig.toml, but no way to do so from the command-line (that I can find in the documentation).

What is the feature you are proposing to solve the problem?

Bun could add CLI args similar to c8's CLI.

• --lines [0-1]: Same as coverageThreshold = { lines = [0-1] }
• --functions [0-100]: Same as coverageThreshold = { functions = [0-1] }
• --all: Same as coverageThreshold = 1

What alternatives have you considered?

Continue as-is and keep bunfig.toml as a single source of truth for coverage configuration.

[jakeboone02]

I put up a draft PR #12436 to address this request, but it depends on #12216 being fixed first.