use image tags to identify channels

this works better with registries like hub.docker.com that don't allow
nested images

.gitlab-ci.yml

@@ -11,11 +11,13 @@ nixos-unstable:
   extends: .build
   variables:
     NIXPKGS_CHANNEL: nixos-unstable
+    IMAGE_TAG: latest
 
 nixos-18.09:
   extends: .build
   variables:
     NIXPKGS_CHANNEL: nixos-18.09
+    IMAGE_TAG: nixos-18.09
 
 # ---- templates ---
 
@@ -26,5 +28,5 @@ nixos-18.09:
     - nix-shell --run .gitlab/push-master
   variables:
     NIX_PATH: "nixpkgs=channel:${NIXPKGS_CHANNEL}"
-    REGISTRY_URL: "${CI_REGISTRY_IMAGE}/${NIXPKGS_CHANNEL}"
+    REGISTRY_URL: "${CI_REGISTRY_IMAGE}"
 

README.md

@@ -26,7 +26,7 @@ image to image.
 # the user must have an account at gitlab
 $ docker login registry.gitlab.com
 # run the curl image which has curl as an entry-point
-$ docker run -ti --rm registry.gitlab.com/zimbatm/docker-nixpkgs/nixos-unstable/curl http://ifconfig.co
+$ docker run -ti --rm registry.gitlab.com/zimbatm/docker-nixpkgs/curl http://ifconfig.co
 180.52.248.114
 ```
 

push-all

@@ -1,12 +1,12 @@
 #!/bin/sh -eu
 
-: "${CI_REGISTRY_IMAGE:=registry.gitlab.com/zimbatm/docker-nixpkgs}"
-: "${REGISTRY_URL:=$CI_REGISTRY_IMAGE/undefined}"
+: "${REGISTRY_URL:=nixpkgs}"
+: "${IMAGE_TAG:=latest}"
 
 releases_json=$(nix-instantiate ./release.nix --strict --eval --json)
 
 for attr in $(echo "$releases_json" | jq -r "keys[]") ; do
   file=$(echo "$releases_json" | jq -r ".\"$attr\"")
   echo "--- $attr -> $file"
-  skopeo copy "docker-archive://$file" "docker://$REGISTRY_URL/$attr:latest"
+  skopeo copy "docker-archive://$file" "docker://$REGISTRY_URL/$attr:$IMAGE_TAG"
 done