Problem:    Fix for recovery and diff mode not tested.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes #8352)

Problem:    Unified diff fails if actually used.
Solution:   Invoke :diffupdate in the test.  Fix the check for working external
            diff. (Ghjuvan Lacambre, Christian Brabandt, closes #8197)

Problem:    Using unified diff is not tested.
Solution:   Test all cases also with unified diff. (issue #8197)

Problem:    'wrap' option is always reset when starting diff mode.
Solution:   Add the "followwrap" item in 'diffopt'. (Rick Howe, closes #7797)

Problem:    Check for features implemented with "if".
Solution:   Use the Check commands. (Ken Takata, closes #7383)

Problem:    Diff and cursorcolumn highlighting don't mix.
Solution:   Fix condition for what attribute to use. (Christian Brabandt,
            closes #7258, closes #7260)

Problem:    Various inconsistencies in test files.
Solution:   Add modelines where they were missing.  Use Check commands instead
            of silently skipping over tests.  Adjust indents and comments.
            (Ken Takata, closes #6695)

Problem:    Removed more than dead code.
Solution:   Put back the decrement.

Problem:    Multiline conceal causes display errors.
Solution:   Do not allow conceal cross over EOL. (closes #6326, closes #4854,
            closes #6302)

Problem:    Line numbers below filler lines not always updated.
Solution:   Don't break out of the win_line() loop too early. (Christian
            Brabandt, closes #6294, closes #6138)