Should apt-get upgrade make a backup while GitLab is online

Pro:

1. Will have smaller installs do the right thing
2. Will prevent disaster when we ship a broken migration

Con:

1. There are many ways to do a backup (snapshots, rsync, etc.)
2. Many installs use more than 50% disk space and will break
3. Making a backup automatically is not done by any other package we know
4. This is not behaviour people expect from packages
5. It will make people wait until the backup is done
6. We do this for every patch release, can be 5 complete copies on disk

/cc @jacobvosmaer @dzaporozhets @JobV

Sytse: I think we should bite the bullet and ensure that migrations don't break installations beyond repair. We recently had a migration that deleted repo's with a . Jacob told me. Stuff like that should always move repo's, don't delete anything.