Fix file changes display in push/pull dialog

Steps to reproduce :

• Do some changes and commit
• Open the push dialog
• Expand the commit to display changes
• Push the commit (without having the changes collapsed)
• Do some changes on different files and commit with a different message than the first one
• Open the push dialog
  => The commit item is reloaded but not the changes, you have to collapse and re-expand the commit to see the correct changes