Update vendored tools/.

tools/vendor/golang.org/x/tools/cmd/goimports/doc.go

@@ -5,9 +5,9 @@ adding missing ones and removing unreferenced ones.
 
      $ go get golang.org/x/tools/cmd/goimports
 
-It's a drop-in replacement for your editor's gofmt-on-save hook.
-It has the same command-line interface as gofmt and formats
-your code in the same way.
+In addition to fixing imports, goimports also formats
+your code in the same style as gofmt so it can be used
+as a replacement for your editor's gofmt-on-save hook.
 
 For emacs, make sure you have the latest go-mode.el:
    https://github.com/dominikh/go-mode.el

tools/vendor/golang.org/x/tools/cmd/goimports/goimports.go

@@ -144,12 +144,19 @@ func processFile(filename string, in io.Reader, out io.Writer, argType argumentT
 			fmt.Fprintln(out, filename)
 		}
 		if *write {
+			if argType == fromStdin {
+				// filename is "<standard input>"
+				return errors.New("can't use -w on stdin")
+			}
 			err = ioutil.WriteFile(filename, res, 0)
 			if err != nil {
 				return err
 			}
 		}
 		if *doDiff {
+			if argType == fromStdin {
+				filename = "stdin.go" // because <standard input>.orig looks silly
+			}
 			data, err := diff(src, res, filename)
 			if err != nil {
 				return fmt.Errorf("computing diff: %s", err)