Nixpkgs: Document nix-store auto-optimize feature

[3noch]

simpson on #nixos pointed out that you can have nix-store optimize the database as its built. This would be great to have in the manual: http://lists.science.uu.nl/pipermail/nix-dev/2015-February/016180.html

[vcunat]

This is wrong repo, and it is documented on the expected place: http://nixos.org/nix/manual/

[3noch]

@vcunat Ah thanks for this. But I'm still not satisfied. The link I posted specifically describes how to enable this feature globally for your store. I think connecting the dots is way too much to ask for the majority of folks (like me). I highly doubt I would have realized it could be enabled globally without that email thread.

[vcunat]

Any suggestion on improving the documentation?

[3noch]

Neither the NixOS nor the Nixpkgs manuals mention auto-optimise-store at all. I'd recommend copying almost the entire email into the Nixpkgs manual and linking to it from the NixOS manual with a minor heading and description. Or possibly the other way around.

I'd be happy to do this if you can recommend a good spot for it.

[vcunat]

I'm inclined that NixOS and Nixpkgs manual should refer to Nix manual as a "prerequisite", as you do have to use nix. Duplicating some brief explanation seems OK to me, but not such details as auto-optimise-store (but the description in Nix manual could be more verbose, I guess).

[3noch]

@vcunat Yah I actually don't care as much where the detail goes. The key is that a nix feature combined with a NixOS/Nixpkgs feature is very valuable, but you have to compose those features entirely by yourself. That's just way too much to ask for most casual users and deserves a bit more exposure. I'm voicing this opinion after several people on #nixos all chimed in and said "That needs to be in the manual."