recent files/folders shouldn't make separate entries for same items in different sides

'recent files/folders' make separate entries for same items in different sides.
it treat 'file 1 - file 2' different than 'file 2 -file 1' and swaping sides make new entry. same for 3way compare.
maybe should only have entry for newest side. if open 'file 1 - file 2' and swap to 'file 2 -file 1', 'recent files/folders' should update to 'file 2 -file 1', not add it.
maybe related to #3090.