2 Seperate Computers Working On The Same Program

I have a large project coming up, and I will be working on it with another PLC programmer, and I am trying to think of the best way where we can both be working on the program, and any changes he makes will be updated on my side (program) and vice versa?

I know if we both go online (for a ControlLogix), his online changes will be automatically updated on my program, but if he needs to make a change that requires him to be offline, those changes will not be on my program.

Just curious if there is another way to keep all (online/offline) changes the same with little effort.

Hi

What we do is keep a master copy so if I am off line the other programmer has the master copy and I only work on a section of the program he is not using.
This means he can work away until I am ready. We would then import the section I was Woking on into the master copy so comments etc are imported.
This same also goes when two of us are working on line I know both will update but not the comments. So again we keep a master copy and at the end if the day we import the sections I was working on into the master copy fit rung comments etc.
Now in ver 21 I understand that the commens can be stored in some CPU but I have not used this yet
some might correct me in that point

Donnchadh