When overwriting files that where already deployed in SharePoint 2010 we normally would write a lot of code to make sure the file got overwritten. One example is here.. Overwrite files in SharePoint 2010 Now with SharePoint 2013 we have an extra property to set in our elements.xml file

 <File Path\="ItemStyleItemStyle.xsl" Url\="ItemStyle.xsl" Type\="GhostableInLibrary" ReplaceContent\="TRUE" Level\="Published"/>

The “ReplaceContent=’True’” will make sure the files get overwritten.