bug#27822: [PATCH] do not auto-remove external packages (fixes #27822)

[Yuri D'Elia <wavexx@thregr.org>]

On Tue, Jul 17 2018, Stefan Monnier wrote:
> AFAIK packages installed via dpkg can't be removed (lack of access
> rights), so attempting to remove them is not that big of a deal, is it?

As described in the bug report, if I add a directory of with custom
packages, autoremove will happily zap all of them because they're not
marked as manually installed.

Additional directories shouldn't be managed by package.el.

> Or does it signal an error, prevent local packages from being
> auto-removed, or something (I mean, beside the philosophical argument,
> does it result in an actual harmful behavior in practice)?

Both. Harmful behavior (deletion) in case there's an additional
directory of user-handled packages. Removal error due to missing
permissions also prevents dependent packages to be auto-removed.