Replicating git history for a file takes 1 merge commit and 3 commits, and this is propably one of the most complex workflows I have encountered:
(might not be correct...)
git checkout -b work
git mv file file.tmp
git commit
git checkout -b copy HEAD^
git mv file file2
git commit
git checkout work # can be skipped if you merge "work" instead.
git merge copy # "work" and "copy" must conflict, stage file.tmp and file2 and commit the result.
git mv file.tmp file
git commit
<git blame is identical for file and file2>
I would love to squash this into a single commit, but git doesn't have a copy operation or detection. :(