git-merge ignore specific files

All,
  I have two branches that are slightly different and
most changes "belong" in both.  There are a handful of
files/directories that are disparate.  Is there any
way in git to tell it not to merge these files?  Kind
of like .gitignore but for merges.
  In addition I'd like a way to specify to git-merge
to leave all merged files unrecorded in the index. 
Then as I go through each file making sure that the
merge "makes sense" (not that git did the right thing;
but that I want the changes in both branches) that I
add the change to the index.
  I'm sure that I'm probably using git "incorrectly"
and I welcome suggestions for modifying my workflow to
a git style.

Any and all suggestions greatly appreciated,

Bill

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