[FEATURE] Allow to push unchecked history

Summary

When packages are dropped from the official repos they do not (neccesarily) have a .SRCINFO file for every commit. It would therefore be good to disable checks for all commits and only check the validity of the latest commit instead.

Description

As we already discussed on IRC it would be great if Package Maintainers could disable the checks for the history of a package in some way. This feature request is related to the discussion in issue devtools#143 regarding the implementation of pkgctl aur export.

One way we came up with was a mechanic similar to setting the AUR_OVERWRITE env var as described in c5302d3a. The referenced commit also mentions AUR_PRIVILEGED, maybe that could be reused.