VMS Help CMS, FETCH, Qualifiers, /MERGE=generation-expression  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Controls whether another generation of the element (called the
    merge generation) is to be merged with the generation that is
    being fetched (called the retrieved generation).

    When you specify the /MERGE qualifier, CMS merges the lines of
    the two generations and delivers a single copy to your default
    directory. The file that is placed in your directory has the
    current creation and revision times. The merge generation cannot
    be on the same line of descent as the retrieved generation. When
    there is a conflict between blocks of one or more lines, CMS
    includes the conflicting lines and flags the conflict.