If there is an update to app-base, apply it first on its own
Currently version updates have to take place over 2 nights, firstly to apply app-base to switch the repos (and it also brings down a lot of other packages), then on the second night it brings down the rest of the packages after the repos have been updated.
I suggest that we change the way it works, so it either does a
yum update app-base first on its own before looking for a list of packages and then doing (in effect) a
yum clean all && yum update.
Alternatively, its current modus operandi is to find a list of available updates first. This list should be checked for app-base. If app-base is in the list then it should update app-base on its own, then loop round again to do a
yum clean all then look for the list of packages to update. Then, as there is no app-base to update, it should continue as before.
This would allow a version update in a single night. It would also have got round the issue we had upgrading to 7.6 Community.