If stdout is a pipe, output to the pipe

If you run micro as `micro | cat` for example, micro will disallow
you from saving the file, and when you quit the buffer, the contents
will be sent to the pipe. This allows one to use micro as part of
an interactive unix pipeline.

Closes #1524

cmd/micro/micro.go

@@ -147,11 +147,16 @@ func LoadInput() []*buffer.Buffer {
 	args := flag.Args()
 	buffers := make([]*buffer.Buffer, 0, len(args))
 
+	btype := buffer.BTDefault
+	if !isatty.IsTerminal(os.Stdout.Fd()) {
+		btype = buffer.BTStdout
+	}
+
 	if len(args) > 0 {
 		// Option 1
 		// We go through each file and load it
 		for i := 0; i < len(args); i++ {
-			buf, err := buffer.NewBufferFromFile(args[i], buffer.BTDefault)
+			buf, err := buffer.NewBufferFromFile(args[i], btype)
 			if err != nil {
 				screen.TermMessage(err)
 				continue
@@ -168,17 +173,22 @@ func LoadInput() []*buffer.Buffer {
 			screen.TermMessage("Error reading from stdin: ", err)
 			input = []byte{}
 		}
-		buffers = append(buffers, buffer.NewBufferFromString(string(input), filename, buffer.BTDefault))
+		buffers = append(buffers, buffer.NewBufferFromString(string(input), filename, btype))
 	} else {
 		// Option 3, just open an empty buffer
-		buffers = append(buffers, buffer.NewBufferFromString(string(input), filename, buffer.BTDefault))
+		buffers = append(buffers, buffer.NewBufferFromString(string(input), filename, btype))
 	}
 
 	return buffers
 }
 
 func main() {
-	defer os.Exit(0)
+	defer func() {
+		if util.Stdout.Len() > 0 {
+			fmt.Fprint(os.Stdout, util.Stdout.String())
+		}
+		os.Exit(0)
+	}()
 
 	// runtime.SetCPUProfileRate(400)
 	// f, _ := os.Create("micro.prof")