Ok ... I finally got it.
So, there is no easy way to generate such a list - and the error message is pretty terrible.
The error should give at least some information, and if possible include the filenames it doesn't like, or at least the line number in the filelist where the problem occurs.
Given a tree like this:
c:\temp\a>dir/s/b/a-d
c:\temp\a\list.txt
c:\temp\a\LEFT\1\2\test.txt
c:\temp\a\LEFT\1\2\testL.txt
c:\temp\a\RIGHT\1\2\test.txt
c:\temp\a\RIGHT\1\2\testR.txt
I need a list like
1\2\test.txt 1\2\testL.txt 1\2\testR.txt
And it isn't very flexible - it requires the same pathnames & filenames on left and right.
With WINDIFF.exe, the list would look like:
c:\temp\a\LEFT\1\2\test.txt c:\temp\a\RIGHT\1\2\test.txt c:\temp\a\LEFT\1\2\testL.txt c:\temp\a\RIGHT\1\2\testR.txt
Allowing for complete paths, and allowing me to specify how files are paired for comparison.
This is pretty useful for version control - where the version numbers are encoded in the filenames, so left and right would never have exactly the same names.