Converting crlf to lf on a single git file

How do I convert a single file that has crlf line returns to have lf line returns in git?

git is already correctly handling crlf to lf conversion automatically for files when I push them to a remote repository, but in this particular case I am not doing a push to a repository. Rather, I am uploading a file, using a file field on an HTML form, to a website that requires that the file have lf line returns. So I need to be able to convert this file individually.

I am on Windows 7.