git - copy a file from another branch

http://stackoverflow.com/questions/2364147/how-to-get-just-one-file-from-another-branch

git checkout master               # first get back to master
git checkout experiment -- app.js # then copy the version of app.js 
                                  # from branch "experiment"

Basically, if we are copying a file, say file1.js from FROM-B branch to TO-B, then:

git  checkout  TO-B
git  checkout  FROM-B  --  file1.js