Comment 6 for bug 1225484

Here's the way I see it working:

If there is a cc mismatch a warning is displayed that says, "custom
columns not the same, some data will not be copied". This warning should
probably only show up once per session per library pair. If the mismatch
is automatically fixable, then the warning should have an "auto fix"
button, that alters the destination library before copying. If the
mismatch is not fixable, or partially fixable, we do nothing.