New feature: File.DuplicateRowTo() duplicate row to specified row position.

DuplicateRowTo() is similar to DuplicateRow() but copies specified row not just after specified source row
but to any other specified position below or above source row.

Also I made minor modifications of tests: using filepath.Join() instead of direct unix-way paths strings
to avoid possible tests fails on other OS.

1 files changed, 37 insertions, 20 deletions

diff --git a/rows.go b/rows.go
index d3fe6e0..3984216 100644
--- a/rows.go
+++ b/rows.go
@@ -376,38 +376,55 @@ func (f *File) InsertRow(sheet string, row int) {
 //    xlsx.DuplicateRow("Sheet1", 2)
 //
 func (f *File) DuplicateRow(sheet string, row int) {
-	if row < 0 {
+	f.DuplicateRowTo(sheet, row, row+1)
+}
+
+// DuplicateRowTo inserts a copy of specified row at specified row position
+// movig down exists rows aftet target position
+//
+//    xlsx.DuplicateRowTo("Sheet1", 2, 7)
+//
+func (f *File) DuplicateRowTo(sheet string, row, row2 int) {
+	if row <= 0 || row2 <= 0 || row == row2 {
 		return
 	}
-	row2 := row + 1
-	f.adjustHelper(sheet, -1, row2, 1)
 
-	xlsx := f.workSheetReader(sheet)
-	idx := -1
-	idx2 := -1
+	ws := f.workSheetReader(sheet)
 
-	for i, r := range xlsx.SheetData.Row {
+	var ok bool
+	var rowCopy xlsxRow
+
+	for i, r := range ws.SheetData.Row {
 		if r.R == row {
-			idx = i
-		} else if r.R == row2 {
-			idx2 = i
-		}
-		if idx != -1 && idx2 != -1 {
+			rowCopy = ws.SheetData.Row[i]
+			ok = true
 			break
 		}
 	}
+	if !ok {
+		return
+	}
 
-	if idx == -1 || (idx2 == -1 && len(xlsx.SheetData.Row) >= row2) {
+	f.adjustHelper(sheet, -1, row2, 1)
+
+	idx2 := -1
+	for i, r := range ws.SheetData.Row {
+		if r.R == row2 {
+			idx2 = i
+			break
+		}
+	}
+	if idx2 == -1 && len(ws.SheetData.Row) >= row2 {
 		return
 	}
-	rowData := xlsx.SheetData.Row[idx]
-	cols := make([]xlsxC, 0, len(rowData.C))
-	rowData.C = append(cols, rowData.C...)
-	f.ajustSingleRowDimensions(&rowData, 1)
+
+	rowCopy.C = append(make([]xlsxC, 0, len(rowCopy.C)), rowCopy.C...)
+	f.ajustSingleRowDimensions(&rowCopy, row2)
+
 	if idx2 != -1 {
-		xlsx.SheetData.Row[idx2] = rowData
+		ws.SheetData.Row[idx2] = rowCopy
 	} else {
-		xlsx.SheetData.Row = append(xlsx.SheetData.Row, rowData)
+		ws.SheetData.Row = append(ws.SheetData.Row, rowCopy)
 	}
 }
 
@@ -446,7 +463,7 @@ func checkRow(xlsx *xlsxWorksheet) {
 			if lenCol < endCol {
 				oldRow := xlsx.SheetData.Row[k].C
 				xlsx.SheetData.Row[k].C = xlsx.SheetData.Row[k].C[:0]
-				tmp := []xlsxC{}
+				var tmp []xlsxC
 				for i := 0; i < endCol; i++ {
 					buffer.WriteString(ToAlphaString(i))
 					buffer.WriteString(strconv.Itoa(endRow))