Undo git mv (rename)
In my case, I moved an entire folder, then realized I should not have.
I really liked @Dave Konopka's answer, but I did not have much success with that approach (maybe my version of GIT (1.8.4)? My files still showed as deleted. I had other changes on the stack that I did not want to lose (unfortunately).
I did have success doing this:
git reset moved_folder
git checkout original_folder
git reset HEAD file2
did the trick for me
If you have done no other changes (that you want to keep) since the last commit, you can do
git reset --hard
Non-cheeky answer:
git mv file2 file1
Updates the index for both old and new paths automatically.
Check documentation of git mv