Made clone (CTRL+B) in code editor clone only the selection.

In code editor, when code is selected, cloning (CTRL+B) now clones only the selected code. The code is cloned to
the end of selection. The previous behaviour was to clone the full line which the selection "touches" to the new
line after the end of selection.

editor/code_editor.cpp

@@ -1060,35 +1060,43 @@ void CodeTextEditor::delete_lines() {
 }
 
 void CodeTextEditor::clone_lines_down() {
+	const int cursor_column = text_editor->cursor_get_column();
 	int from_line = text_editor->cursor_get_line();
 	int to_line = text_editor->cursor_get_line();
-	int column = text_editor->cursor_get_column();
-
+	int from_column = 0;
+	int to_column = 0;
+	int cursor_new_line = to_line + 1;
+	int cursor_new_column = text_editor->cursor_get_column();
+	String new_text = "\n" + text_editor->get_line(from_line);
+	bool selection_active = false;
+
+	text_editor->cursor_set_column(text_editor->get_line(from_line).length());
 	if (text_editor->is_selection_active()) {
+		from_column = text_editor->get_selection_from_column();
+		to_column = text_editor->get_selection_to_column();
+
 		from_line = text_editor->get_selection_from_line();
 		to_line = text_editor->get_selection_to_line();
-		column = text_editor->cursor_get_column();
+		cursor_new_line = to_line + text_editor->cursor_get_line() - from_line;
+		cursor_new_column = to_column == cursor_column ? 2 * to_column - from_column : to_column;
+		new_text = text_editor->get_selection_text();
+		selection_active = true;
+
+		text_editor->cursor_set_line(to_line);
+		text_editor->cursor_set_column(to_column);
 	}
-	int next_line = to_line + 1;
 
-	bool caret_at_start = text_editor->cursor_get_line() == from_line;
 	text_editor->begin_complex_operation();
+
 	for (int i = from_line; i <= to_line; i++) {
 		text_editor->unfold_line(i);
-		text_editor->set_line(next_line - 1, text_editor->get_line(next_line - 1) + "\n");
-		text_editor->set_line(next_line, text_editor->get_line(i));
-		next_line++;
-	}
-
-	if (caret_at_start) {
-		text_editor->cursor_set_line(to_line + 1);
-	} else {
-		text_editor->cursor_set_line(next_line - 1);
 	}
-
-	text_editor->cursor_set_column(column);
-	if (text_editor->is_selection_active()) {
-		text_editor->select(to_line + 1, text_editor->get_selection_from_column(), next_line - 1, text_editor->get_selection_to_column());
+	text_editor->deselect();
+	text_editor->insert_text_at_cursor(new_text);
+	text_editor->cursor_set_line(cursor_new_line);
+	text_editor->cursor_set_column(cursor_new_column);
+	if (selection_active) {
+		text_editor->select(to_line, to_column, 2 * to_line - from_line, 2 * to_column - from_column);
 	}
 
 	text_editor->end_complex_operation();