Record where a package was installed from

[R. Diez]

Hi all:

Recently I had some trouble because MELPA had dropped package etags-select. There was no warning within Emacs. My usual configuration just 
failed on a new machine.

One of reasons why this was not immediately obvious is that the package manager does not record where a package was installed from. As far 
as I know, there is no warning when an installed package is no longer available in any repository either (which means it will no longer be 
updated). On Linux, the Synaptic package manager has a way to find out what installed packages came from a certain repository.

At first, I thought this was a limitation in the Paradox package manager, so I 
filed a bug against it:

https://github.com/Malabarba/paradox/issues/172

But it turns out that this is a fundamental limitation in the Emacs core 
package manager (see that bug report for more information).

Is this correct? If so, I guess the first step would be to record where a package came from. That in itself should not be hard to achieve. I 
am sure that Paradox etc. will then move to display the package source in a table column.

Regards,
  rdiez