How to enable notifications in Force.com IDE that file was modified on server? Now several people in the project work with one class and we just simply overwriting each other code..
I believe there is no such notification available. But you can avoid overwriting. Before saving the file to server,right click on the file and do Force.com>Synchronize with server.
It will open the "Team Synchronizing" perspective. Then click on the down arrow in navigation panel (Shown below).
This will open a comparison view of your local file and remote file. Copy all the changes (Except your local changes) from server to your local file. Then save your file to server.
In this way you can avoid overwrite. Hope this will help.
I think there is no such feature available from salesforce to work for a same class and notified if changes occur so working on a same class at same time is not possible for two developers. Force.com Eclipse IDE itself provide an Error Message telling that Apex/VFpage File on server is updated and your current file is not in synch. You can try testing this out with simple experiment
Step 1: Synch a salesforce project in Force.com Eclipse IDE
Step 2: Update a VFpage/trigger/apex class in salesforce directly from browser.
Step 3: open the file in Eclipse IDE and try editing and saving it again. you will get a small yellow error with the message.