I Was getting the below error while trying to merge the DEV branch changes to Main branch. In my case, the DEV branch was newly created after the PU upgrade (10.0.12) and trying to merge the new changes to Main. I was doing the merger in my Development remote server.
The item $/D365FO/Trunk/Main/ has an incompatible pending change. See output tool window for information on any other errors.
Reasons:
-> The main branch is not having the latest code of that object
-> Any pending changes to check in for that particular object in Main branch and trying to merge the code for the same object from DEV.
Solution:
-> Check-in any pending changes in Main branch
-> Download the latest changes from Main branch
-> Make sure there are no pending changes to check-in
-> Now, perform the code merger from DEV to MAIN.
@Rahul