buildSourceUrl
fun buildSourceUrl(rootDir: Path, file: String, fileLine: Int, context: CodeBrowserUrl.Context): String?
Returns the <baseUrl>/blob/<commit>/<encoded-path>[#L<line>] URL for a local file, or null if the file isn't inside the git root (no link makes sense outside the tracked tree).
file may be absolute or relative. Relative paths are resolved against rootDir. Inputs that fail to parse as a Path return null instead of throwing.