Add local path to nixpkgs to avoid constant nixpkgs download

Author: tomberek

manage

@@ -58,7 +58,10 @@ state_file="$here/${deployment}.nixops"
 
 source "$here/nixpkgs-version.sh"
 
-export NIX_PATH=nixpkgs="$nixpkgs_snapshot":"$repo_root":.
+function colon(){
+    echo ${1:+${1}:}
+}
+export NIX_PATH=nixpkgs="$(colon $nixpkgs_cache)$(colon $nixpkgs_snapshot)$repo_root":.
 export NIXOPS_STATE="$state_file"
 export NIXOPS_DEPLOYMENT="$deployment"
 

nixpkgs-version.nix

@@ -6,9 +6,10 @@
 #   1. Choose a channel and click on it.
 #   2. Get the URL of the `nixexprs.tar.xz` file for the channel.
 #   4. Paste the URL below for `url`.
-#   5. Get SHA256 hash of URL contents with `nix-prefetch-url --unpack <url>`.
+#   5. Get SHA256 hash and cache path of URL contents with `nix-prefetch-url --unpack <url>`.
 
 {
-  url    = "https://d3g5gsiof5omrk.cloudfront.net/nixpkgs/nixpkgs-17.03pre101896.4a524cf/nixexprs.tar.xz";
-  sha256 = "1wrm9k0plpzz0wi94ry1xv1v3aq4vs20v5dzxv4azn4i8vhf7wmg";
+  url    = "https://d3g5gsiof5omrk.cloudfront.net/nixpkgs/nixpkgs-18.03pre126798.42b9b8f7c86/nixexprs.tar.xz";
+  sha256 = "0yf4z49zm7bc55cgdhdzfqqyrlnkckg2hfmwd78w4i9sw89nbxp3";
+  cache  = "/nix/store/6k4mwhwnq72dgn83ahgws33fsy31ff13-nixexprs.tar.xz";
 }

nixpkgs-version.sh

@@ -3,7 +3,9 @@
 here=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
 
 nixpkgs_snapshot=$(eval echo "$(nix-instantiate --eval -E "(import \"$here/nixpkgs-version.nix\").url")")
+nixpkgs_cache=$(eval echo "$(nix-instantiate --eval -E "(import \"$here/nixpkgs-version.nix\").cache")")
 export nixpkgs_snapshot
+export nixpkgs_cache
 export nixops_version="nixops"
 
 # Or you can use a more recent build of nixops: