apt {upgrade,install, source} require an update call first

I think that this should be tracked in its own separate bug tracking my specific UX objection to the current status quo.

See https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1429285/comments/5, subsequent discussion and https://twitter.com/chr1sa/status/894048628284604416

We think that the updating of indexes should be an implementation detail of "apt upgrade" and "apt install", rather than something exposed to the user. If updating is judged be required (for example the index is more than X old), then it should be done automatically before the requested operation commences.

Here's one proposed implementation:

1) Fix bug 1429285 ("apt-get update --if-necessary").

2) Add an option to have "apt install" and "apt upgrade" (also "apt full-upgrade", etc?) automatically and internally call the implementation of "apt-get update --if-necessary" first.

3) Enable the option by default on Ubuntu.

This would change the behaviour of "apt", which AIUI is intended to be the user focused CLI. It wouldn't change the behaviour of "apt-get", which AIUI needs to retain behavioural backwards compatibility for existing scripts.

Then we could promote "apt install" and "apt upgrade" as much simpler commands to operate.

Note that Julian disagreed with this proposed behaviour change in https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1429285/comments/7. I think that the very user-focused Ubuntu perspective should be to focus on the common use case for "apt". Hence my (compromise) suggestion that we implement this as an option upstream, and then leave it to distros to choose the default behaviour for their users.