is a "- *.ext" filter overriden by a later "+ *.ext"

[Louis-David Mitterrand]

Hi,

In our backup script we sometimes would like to override the common
(i.e: static) excludes filter list. For example we exclude "- *.ext" for
all backups but would like to include "+ *.ext" only for 'local'
backups. 

Are such entries supposed to cancel each other? How can one override an
earlier exclude in a filter list?

Thanks,