* lisp/gnus/gnus-sum.el (gnus-dependencies-add-header): Code is
correct, but docs had logic of `gnus-summary-ignore-duplicates'
backwards: if it's t, the Message-IDs will not be renamed.
If FORCE-NEW is not nil, enter HEADER into the DEPENDENCIES table even
if it was already present.
-If `gnus-summary-ignore-duplicates' is nil then duplicate Message-IDs
-will not be entered in the DEPENDENCIES table. Otherwise duplicate
-Message-IDs will be renamed to a unique Message-ID before being
-entered.
+If `gnus-summary-ignore-duplicates' is non-nil then duplicate
+Message-IDs will not be entered in the DEPENDENCIES table.
+Otherwise duplicate Message-IDs will be renamed to a unique
+Message-ID before being entered.
Returns HEADER if it was entered in the DEPENDENCIES. Returns nil otherwise."
(let* ((id (mail-header-id header))