fix(readline): take into account newlines when calculating amount of lines taken up by input

this does not really fix the issue of multiline input
being broken completely, but prevents the prompt
being reprinted on input

readline/update.go

@@ -1,6 +1,10 @@
 package readline
 
-import "golang.org/x/text/width"
+import (
+	"strings"
+
+	"golang.org/x/text/width"
+)
 
 // updateHelpers is a key part of the whole refresh process:
 // it should coordinate reprinting the input line, any Infos and completions
@@ -52,19 +56,19 @@ func (rl *Instance) updateReferences() {
 	rl.posY = 0
 	rl.fullY = 0
 
-	var fullLine, cPosLine int
+	var curLine []rune
 	if len(rl.currentComp) > 0 {
-		fullLine = getWidth(rl.lineComp)
+		curLine = rl.lineComp
-		cPosLine = getWidth(rl.lineComp[:rl.pos])
 	} else {
-		fullLine = getWidth(rl.line)
+		curLine = rl.line
-		cPosLine = getWidth(rl.line[:rl.pos])
 	}
+	fullLine := getWidth(curLine)
+	cPosLine := getWidth(curLine[:rl.pos])
 
 	// We need the X offset of the whole line
 	toEndLine := rl.promptLen + fullLine
 	fullOffset := toEndLine / GetTermWidth()
-	rl.fullY = fullOffset
+	rl.fullY = fullOffset + strings.Count(string(curLine), "\n")
 	fullRest := toEndLine % GetTermWidth()
 	rl.fullX = fullRest