[Nix-dev] updates and nix-env -i vs nix-env -iA

[Peter Simons]

Hi Florian,

 > Could we, apart from having buildEnv, do something about nix-env
 > remembering how things were installed?
 >
 > As far as I understand, "nix-env -u" does not care about attr-paths, but
 > searches for updates based on attr-name.
 >
 > 1) nix-env -i python
 > - attr-path: pkgs.pythonFull
 >
 > 2) nix-env -i python-2.7.1
 > - attr-path: pkgs.python27 and pkgs.python
 >
 > 3) nix-env -iA pkgs.python27
 > - attr-path: pkgs.python27
 >
 > "nix-env -u" could remember the attr-path and use that to search for
 > updates.

it would be nice if nix-env could remember and re-use attribute names.
The problem I see, though, is that attribute names change a lot over
time. Granted, the name pythonFull is probably not going to change, but
that is a special case. In general, how should nix-env respond when it
detects that an attribute path has disappeared?

Take care,
Peter