GNU Interactive Tools
3.1.8.8 Selecting files matching patterns
If the very first character in the input line is a `+', what comes after
it is considered a (space separated) list of shell patterns, and all the
files that match at least one pattern from that list will be marked as
selected. An empty list of shell patterns (i.e. the `+' by itself) will
cause all the files to be selected.
If the very first character in the input line is a `-', the space
separated list of shell patterns that follows is used to unselect files.
An empty list of shell patterns (i.e. the `-' by itself) will cause all
the selected files to be unselected.
Finally, if the first and only character in the input line is a `*',
then all the selected files will become unselected, and all the
unselected files will become selected.
