Steps to Reproduce

1. export a blank book and import the exported book
2. check the number of the default cell style of the book

Current Result

2

Expected Result

1

Debug Information

• check keikai.test > io.keikai.model.ExporterTest.defaultCellStyle() at branch keikai-803

Use case

• this bug produces a large size of styles.xml. The real use case is 424 MB
• the user imports and exports the same xlsx file repeatedly and produces a large number of (redundant) default cell styles.
• When opening such a file with lots of default cell styles In Excel, all cell styles are lost, no color, font size, border, filter. But keikai still can render those cell styles correctly.

Workaround -repair the file

1. import the file into keikai and clear the file redundant default styles
   See ClearStyleComposer.java
2. export the file
3. open the exported file in Excel.
4. Excel will prompt you to repair it.
5. repair it and save the file again