possible 'git cp'/how does git detect copies

I was looking today at duplicating a file but, I soon realized that there is no 'git cp' command (this was the "deductive approach to git commands", starting from git mv/rm/...). How does "git diff -C" detect copies (-C is used for this, according to the documentation)?

On a very simple test, I couldn't see this working. I just copied one file, added it, committed the change, ran "git diff -C HEAD^!". There is no place saying that it's contents is copied from some other file (both files are in the repository now).

"git blame -C new_copied_file" also doesn't show the commits for the original file.

This is all with 1.5.6.1.

I am probably missing something here... but I can't produce an example of copied contents that actually works. Any hint would be appreciated.

I found this older thread [1] on "git cp" but the discussion appears to have stalled at some point. If there is indeed no use of a "git cp" command, I would like at least some info on how content copies are being detected, since I haven't seen this working.

[1] http://kerneltrap.org/mailarchive/git/2008/2/3/705424

Many thanks, Mircea

-- http://mircea.bardac.net