Ensure inactive tabs are force-updated after FocusGained.
Ensure inactive tabs are force-updated after FocusGained.

On FocusGained the current tab is force-updated.  If there are any other
tabs, we want to make sure they are also force-updated when the user
next switches to them.  To do this we set a flag which is read and
cleared on TabEnter.

See #525.

airblade/vim-gitgutter