Comment 5 for bug 1225484

I am in favor of the warning, and less in favor of optional creation. In particular, I am concerned about type mismatches, where #foo is text/single in one and text/multiple in the other. The column cannot be created because it is already there, and changing its type isn't possible (or a good idea). Because of this, column creation would be partial. Columns with type mismatches would still not copy.

Of course, the warning dialog could separate the two cases, but that could be more confusing than warning and leaving the fix to the user.

All the above notwithstanding, if you want the option to create the missing columns added, I can do that.