If you do git log --patch -- path/to/file, you will get the history of the file along with a diff of all the changes made to it with each commit, like this:
The following URL will show all the commits for a single file in a format similar to git log -p:
http://github.com/
...where:
is the username of the person that owns the repo is the repo name can be 'master' or any other branch is hopefully self-explanatoryPicking at (somewhat) random, here is an example from the vim-fugitive repo.