Click on the Merge Generation button to specify that
  another generation of the element (called the merge
  generation) is to be merged with the generation being
  fetched (called the retrieved generation).

  Fill in the Merge Generation field with the number of the
  merge generation.

  CMS merges the lines of the two generations and delivers
  a single copy of the file to your default directory.

  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.