It is possible to ask CVS who is currently editing a file, but it only works if the developers announce to CVS when they intend to edit a file. It should be decided at project startup if this model is to be used.
To use this model, developers should check out the module read only. It can be done by checking Checkout read-only in the Globals tab of every WinCvs dialog. This is checked by default.
To edit a file, do the following:
Select the file you want to edit.
Choose the Trace -> Edit selection menu item. (Alternatively, use the shortcut in the toolbar.) The read-only flag will be removed, and the CVS server registers you as an editor of the given file.
Edit the file (doubleclick it).
Commit the file as described in Sending Your Changes to CVS.
When you commit the file, the CVS server assumes you are no longer editing it, and WinCvs will make the file read only again. If you did not make any changes, a commit will not tell the CVS server that your have finished editing it. In that case you should rather do the following:
Select the file you marked for editing.
Click the right mouse button on the selction, and choose the Trace -> Unedit selection menu item (Alternatively, use the shortcut in the toolbar).
And now, back to the original question: "Who's editing that file?" To list the editor(s) if any of a file, do this:
Select the file you are curious about.
Click the right mouse button on the selction, and choose the Trace -> Editors menu item (Alternatively, use the shortcut in the toolbar).
WinCvs will now list the known editors of the file.