So it turns out this _can_ happen, without an in-script coding error.
Consider the behavior of a script with overlapping by/field fields:
$ cat test.csv
a,b
x,2
x,1
x,1
$ ./scripts/csv.py test.csv -ba -bb -fb
During the first fold, rows 2 and 3 will contain b=1, but during the
second fold they will have been merged, resulting in b=2.
So, relaxing to a warning for now. Maybe the table renderer should be
rewritten to avoid folding? (note diffing results may be tricky)
Christopher Haster
a3082437df