Projects can be shared in team repositories (CVS, Subversion, etc.). Team members can then easily work together, as the platform supports required collaborative actions:
We recommend users to read the Eclipse Team CVS tutorial to get familiar with collaborative work in Eclipse.
Even if you do not setup a team repository, you still have access to the Local History of the files edited in the workspace:
A dialog shows up and lets you compare the contents of the edited file with past versions. This dialog computes the textual difference and a structural difference (added or removed functions).
Team CVS tutorial