Git merge selectively from different branch

gistfile1.txt

$ git branch
* master
  twitter_integration
$ git checkout twitter_integration app/models/avatar.rb db/migrate/20090223104419_create_avatars.rb test/unit/models/avatar_test.rb test/functional/models/avatar_test.rb
$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   new file:   app/models/avatar.rb
#   new file:   db/migrate/20090223104419_create_avatars.rb
#   new file:   test/functional/models/avatar_test.rb
#   new file:   test/unit/models/avatar_test.rb
#
$ git commit -m "'Merge' avatar code from 'twitter_integration' branch"

from http://jasonrudolph.com/blog/2009/02/25/git-tip-how-to-merge-specific-files-from-another-branch/

To compare a file between two branches:
git diff mybranch master -- myfile.cs