Eclipse git checkout (aka, revert)
This can be done via the context menu "Replace with/File in Git index" on the file in package view.
You can achieve this by doing a (hard) reset. On the project's context menu, select Team > Reset to..., choose "HEAD" and "Hard" as reset type.
Please note that doing this you will lose the changes of ALL files. To revert just a single file see this answer.
in Eclipse Version: 3.7.0
in "Team Synchronizing perspective" --> right click on file/folder in synchronize view --> overwrite