Matching omits singular results that must still form a master/merge document

[anthony-gray]

Matching omits singular results that must still form a master/merge document. For example, if matching on id1 and id2 for:
a. 1.xml with id1=1 and id2=A
b. 2.xml with id1=2 and id2=A
c. 3.xml with id1=1 and id2=C
d. 4.xml with id1=4 and id2=D
the matches should be {[1.xml, 2.xml, 3.xml], [4.xml]}, but are instead {[1.xml, 2.xml, 3.xml]}.