The problem with deferring the situation to the clean command is that the system appears to be working properly with no problem, and the user will have to _guess_ that cleanup is required.
Running md5sum on the packages is not expensive:
ubuntu@T000000-tx2b:/var/lib/apt/lists$ time md5sum ports.ubuntu.com_ubuntu-ports_dists_xenial_universe_binary-arm64_Packages
005695bf761c4719325927b5a236a77e ports.ubuntu.com_ubuntu-ports_dists_xenial_universe_binary-arm64_Packages
real 0m0.166s
user 0m0.136s
sys 0m0.036s
Certainly it's much faster than the downloading of the indexes in the first place.
The problem with deferring the situation to the clean command is that the system appears to be working properly with no problem, and the user will have to _guess_ that cleanup is required.
Running md5sum on the packages is not expensive:
ubuntu@ T000000- tx2b:/var/ lib/apt/ lists$ time md5sum ports.ubuntu. com_ubuntu- ports_dists_ xenial_ universe_ binary- arm64_Packages 9325927b5a236a7 7e ports.ubuntu. com_ubuntu- ports_dists_ xenial_ universe_ binary- arm64_Packages
005695bf761c471
real 0m0.166s
user 0m0.136s
sys 0m0.036s
Certainly it's much faster than the downloading of the indexes in the first place.