Copy env files to remote hosts

Setting env variables in the docker arguments requires having them on
the deploy host.

Instead we'll add two new commands `kamal env push` and
`kamal env delete` which will manage copying the environment as .env
files to the remote host.

Docker will pick up the file with `--env-file <path-to-file>`. Env files
will be stored under `<kamal run directory>/env`.

Running `kamal env push` will create env files for each role and
accessory, and traefik if required.

`kamal envify` has been updated to also push the env files.

By avoiding using `kamal envify` and creating the local and remote
secrets manually, you can now avoid accessing secrets needed
for the docker runtime environment locally. You will still need build
secrets.

One thing to note - the Docker doesn't parse the environment variables
in the env file, one result of this is that you can't specify multi-line
values - see https://github.com/moby/moby/issues/12997.

We maybe need to look docker config or docker secrets longer term to get
around this.

Hattip to @kevinmcconnell - this was all his idea.

lib/kamal/commands/accessory.rb

@@ -86,14 +86,6 @@ class Kamal::Commands::Accessory < Kamal::Commands::Base
     end
   end
 
-  def make_directory_for(remote_file)
-    make_directory Pathname.new(remote_file).dirname.to_s
-  end
-
-  def make_directory(path)
-    [ :mkdir, "-p", path ]
-  end
-
   def remove_service_directory
     [ :rm, "-rf", service_name ]
   end
@@ -106,6 +98,14 @@ class Kamal::Commands::Accessory < Kamal::Commands::Base
     docker :image, :rm, "--force", image
   end
 
+  def make_env_directory
+    make_directory accessory_config.host_env_directory
+  end
+
+  def remove_env_file
+    [:rm, "-f", accessory_config.host_env_file_path]
+  end
+
   private
     def service_filter
       [ "--filter", "label=service=#{service_name}" ]

lib/kamal/commands/app.rb

@@ -81,7 +81,7 @@ class Kamal::Commands::App < Kamal::Commands::Base
     docker :run,
       ("-it" if interactive),
       "--rm",
-      *config.env_args,
+      *role&.env_args,
       *config.volume_args,
       *role&.option_args,
       config.absolute_image,
@@ -149,6 +149,13 @@ class Kamal::Commands::App < Kamal::Commands::Base
     docker :tag, config.absolute_image, config.latest_image
   end
 
+  def make_env_directory
+    make_directory config.role(role).host_env_directory
+  end
+
+  def remove_env_file
+    [:rm, "-f", config.role(role).host_env_file_path]
+  end
 
   private
     def container_name(version = nil)

lib/kamal/commands/base.rb

@@ -26,6 +26,14 @@ module Kamal::Commands
       docker :container, :ls, *("--all" unless only_running), "--filter", "name=^#{container_name}$", "--quiet"
     end
 
+    def make_directory_for(remote_file)
+      make_directory Pathname.new(remote_file).dirname.to_s
+    end
+
+    def make_directory(path)
+      [ :mkdir, "-p", path ]
+    end
+
     private
       def combine(*commands, by: "&&")
         commands

lib/kamal/commands/traefik.rb

@@ -1,5 +1,5 @@
 class Kamal::Commands::Traefik < Kamal::Commands::Base
-  delegate :argumentize, :argumentize_env_with_secrets, :optionize, to: Kamal::Utils
+  delegate :argumentize, :env_file_with_secrets, :optionize, to: Kamal::Utils
 
   DEFAULT_IMAGE = "traefik:v2.9"
   CONTAINER_PORT = 80
@@ -63,6 +63,22 @@ class Kamal::Commands::Traefik < Kamal::Commands::Base
     "#{host_port}:#{CONTAINER_PORT}"
   end
 
+  def env_file
+    env_file_with_secrets config.traefik.fetch("env", {})
+  end
+
+  def host_env_file_path
+    File.join host_env_directory, "traefik.env"
+  end
+
+  def make_env_directory
+    make_directory(host_env_directory)
+  end
+
+  def remove_env_file
+    [:rm, "-f", host_env_file_path]
+  end
+
   private
     def publish_args
       argumentize "--publish", port unless config.traefik["publish"] == false
@@ -73,13 +89,11 @@ class Kamal::Commands::Traefik < Kamal::Commands::Base
     end
 
     def env_args
-      env_config = config.traefik["env"] || {}
+      argumentize "--env-file", host_env_file_path
+    end
 
-      if env_config.present?
-        argumentize_env_with_secrets(env_config)
-      else
-        []
-      end
+    def host_env_directory
+      File.join config.host_env_directory, "traefik"
     end
 
     def labels