Hi, this is a plea to retain versioned copies of the org-plus-contrib
tar in the <https://orgmode.org/elpa/> directory, because package
managers refer to them. Currently, the only versions present at that
location are 20171227 and 20171228.

I'm using NixOS, and my current nixpkgs tree refers to 20170911, which
cannot (re)-build now because the source is missing. Here's the Nix
specification referencing the now-broken URL:

<https://github.com/NixOS/nixpkgs-channels/blob/nixos-17.09/pkgs/applications/editors/emacs-modes/org-generated.nix>

The latest nixpkgs master does have it updated to 20171225 -- which is
*also* a broken link, just a week later. (And I prefer to use a 'stable'
channel rather than master.)

<https://github.com/NixOS/nixpkgs/blob/afac8c61e9542ad04cd9da0cd53f2e2aaaf1aeab/pkgs/applications/editors/emacs-modes/org-generated.nix>

I don't necessarily expect orgmode.org to retain these sources
indefinitely, but deleting them after a couple of weeks or months causes
all sorts of headaches.

Thanks for the consideration!

CL