Suggestion for package.el: atomic package-upgrade

[dqs7cp2e]

The current `package-upgrade' from package.el delete old package
before installing the new one. This can be problematic if the user
interrupt the process or if there is some network problems.

`package-install' allow the same package to be installed if the
argument is `package-desc' instead symbol representing package name.
This allow package to be upgraded atomically. Is this a bad idea?

package-upgrade--diff.txt
Description: Text document