Re: Mark in dired-diff

[Richard M. Stallman]

    When dired-dwim-target is t (which uses the name of a dired buffer
    displayed in the next window in the prompt), the mark in the current
    dired buffer makes it impossible for dired-diff to insert the directory
    name from the next window as the default value in the minibuffer.
    That's because the mark in the current buffer takes precedence over
    the value of dired-dwim-target.

Perhaps it should ignore the mark when the mark is on the current
line--to make it similar to the other case we were just discussing.