Merge pull request swiftlang#155 from dylansturg/quieter_formatting

Don't propagate the diagnostic engine when formatting.

Author: allevato

Sources/swift-format/Run.swift

@@ -77,7 +77,10 @@ func formatMain(
   configuration: Configuration, sourceFile: FileHandle, assumingFilename: String?, inPlace: Bool,
   debugOptions: DebugOptions, diagnosticEngine: DiagnosticEngine
 ) -> Int {
-  let formatter = SwiftFormatter(configuration: configuration, diagnosticEngine: diagnosticEngine)
+  // Even though `diagnosticEngine` is defined, it's use is reserved for fatal messages. Pass nil
+  // to the formatter to suppress other messages since they will be fixed or can't be automatically
+  // fixed anyway.
+  let formatter = SwiftFormatter(configuration: configuration, diagnosticEngine: nil)
   formatter.debugOptions = debugOptions
   let assumingFileURL = URL(fileURLWithPath: assumingFilename ?? "<stdin>")