include
.RS 4
.TP 4
-.B \-\-output=(messages|threads)
+.B \-\-output=(messages|threads|files)
.RS 4
.TP 4
Output the number of matching threads.
.RE
+.RS 4
+.TP 4
+.B files
+
+Output the number of files associated with matching messages. This may
+be bigger than the number of matching messages due to duplicates
+(i.e. multiple files having the same message-id).
+.RE
.RE
.RS 4