Report merged lines as changed block if possible, not as a sequence of added/deleted blocks. To facilitate access to merge parent lines AddBlock got mergeLineAt() method that reports index of the line in the second parent (if any), while insertedAt() has been changed to report index in the first parent always

[section1]
# comment
key1=value 1
key2=value 2
key3=value 3#comment

%include ./included.rc

[section3]
key1=value 1-3

[section1]
key4=value 4
%unset key1