squash merge from dev branch

vendor/gopkg.in/alecthomas/kingpin.v2/guesswidth_unix.go

@@ -0,0 +1,38 @@
+// +build !appengine,linux freebsd darwin dragonfly netbsd openbsd
+
+package kingpin
+
+import (
+	"io"
+	"os"
+	"strconv"
+	"syscall"
+	"unsafe"
+)
+
+func guessWidth(w io.Writer) int {
+	// check if COLUMNS env is set to comply with
+	// http://pubs.opengroup.org/onlinepubs/009604499/basedefs/xbd_chap08.html
+	colsStr := os.Getenv("COLUMNS")
+	if colsStr != "" {
+		if cols, err := strconv.Atoi(colsStr); err == nil {
+			return cols
+		}
+	}
+
+	if t, ok := w.(*os.File); ok {
+		fd := t.Fd()
+		var dimensions [4]uint16
+
+		if _, _, err := syscall.Syscall6(
+			syscall.SYS_IOCTL,
+			uintptr(fd),
+			uintptr(syscall.TIOCGWINSZ),
+			uintptr(unsafe.Pointer(&dimensions)),
+			0, 0, 0,
+		); err == 0 {
+			return int(dimensions[1])
+		}
+	}
+	return 80
+}