Combine multiarch and native/cache builders

Combine the two builders, as they are almost identical. The only
difference was whether the platforms were set.

The native cached builder wasn't using the context it created, so now
we do.

We'll set the driver to `docker-container` - it seems to be the default
but the Docker docs claim it is `docker`.

lib/kamal/commands/builder.rb

@@ -11,22 +11,17 @@ class Kamal::Commands::Builder < Kamal::Commands::Base
   end
 
   def target
-    if config.builder.multiarch?
-      if config.builder.remote?
-        if config.builder.local?
-          multiarch_remote
-        else
-          native_remote
-        end
-      else
-        multiarch
-      end
+    case
+    when !config.builder.multiarch? && !config.builder.cached?
+      native
+    when !config.builder.multiarch? && config.builder.cached?
+      local
+    when config.builder.local? && config.builder.remote?
+      multiarch_remote
+    when config.builder.remote?
+      native_remote
     else
-      if config.builder.cached?
-        native_cached
-      else
-        native
-      end
+      local
     end
   end
 
@@ -34,16 +29,12 @@ class Kamal::Commands::Builder < Kamal::Commands::Base
     @native ||= Kamal::Commands::Builder::Native.new(config)
   end
 
-  def native_cached
-    @native ||= Kamal::Commands::Builder::Native::Cached.new(config)
-  end
-
   def native_remote
     @native ||= Kamal::Commands::Builder::Native::Remote.new(config)
   end
 
-  def multiarch
-    @multiarch ||= Kamal::Commands::Builder::Multiarch.new(config)
+  def local
+    @local ||= Kamal::Commands::Builder::Local.new(config)
   end
 
   def multiarch_remote

lib/kamal/commands/builder/base.rb

@@ -5,7 +5,10 @@ class Kamal::Commands::Builder::Base < Kamal::Commands::Base
   ENDPOINT_DOCKER_HOST_INSPECT = "'{{.Endpoints.docker.Host}}'"
 
   delegate :argumentize, to: Kamal::Utils
-  delegate :args, :secrets, :dockerfile, :target, :local_arch, :local_host, :remote_arch, :remote_host, :cache_from, :cache_to, :ssh, to: :builder_config
+  delegate \
+    :args, :secrets, :dockerfile, :target, :local_arch, :local_host, :remote_arch, :remote_host,
+    :cache_from, :cache_to, :multiarch?, :ssh,
+    to: :builder_config
 
   def clean
     docker :image, :rm, "--force", config.absolute_image

lib/kamal/commands/builder/local.rb

@@ -1,6 +1,6 @@
-class Kamal::Commands::Builder::Multiarch < Kamal::Commands::Builder::Base
+class Kamal::Commands::Builder::Local < Kamal::Commands::Builder::Base
   def create
-    docker :buildx, :create, "--use", "--name", builder_name
+    docker :buildx, :create, "--name", builder_name, "--driver=docker-container"
   end
 
   def remove
@@ -16,7 +16,7 @@ class Kamal::Commands::Builder::Multiarch < Kamal::Commands::Builder::Base
   def push
     docker :buildx, :build,
       "--push",
-      "--platform", platform_names,
+      *platform_options,
       "--builder", builder_name,
       *build_options,
       build_context
@@ -28,14 +28,16 @@ class Kamal::Commands::Builder::Multiarch < Kamal::Commands::Builder::Base
 
   private
     def builder_name
-      "kamal-#{config.service}-multiarch"
+      "kamal-local"
     end
 
-    def platform_names
-      if local_arch
-        "linux/#{local_arch}"
-      else
-        "linux/amd64,linux/arm64"
+    def platform_options
+      if multiarch?
+        if local_arch
+          [ "--platform", "linux/#{local_arch}" ]
+        else
+          [ "--platform", "linux/amd64,linux/arm64" ]
+        end
       end
     end
 end

lib/kamal/commands/builder/multiarch/remote.rb

@@ -1,4 +1,4 @@
-class Kamal::Commands::Builder::Multiarch::Remote < Kamal::Commands::Builder::Multiarch
+class Kamal::Commands::Builder::Multiarch::Remote < Kamal::Commands::Builder::Base
   def create
     combine \
       create_contexts,
@@ -12,6 +12,21 @@ class Kamal::Commands::Builder::Multiarch::Remote < Kamal::Commands::Builder::Mu
       super
   end
 
+  def info
+    combine \
+      docker(:context, :ls),
+      docker(:buildx, :ls)
+  end
+
+  def push
+    docker :buildx, :build,
+      "--push",
+      *platform_options,
+      "--builder", builder_name,
+      *build_options,
+      build_context
+  end
+
   def context_hosts
     chain \
       context_host(builder_name_with_arch(local_arch)),
@@ -24,7 +39,7 @@ class Kamal::Commands::Builder::Multiarch::Remote < Kamal::Commands::Builder::Mu
 
   private
     def builder_name
-      super + "-remote"
+      "kamal-#{config.service}-multiarch-remote"
     end
 
     def builder_name_with_arch(arch)
@@ -58,4 +73,12 @@ class Kamal::Commands::Builder::Multiarch::Remote < Kamal::Commands::Builder::Mu
     def remove_context(arch)
       docker :context, :rm, builder_name_with_arch(arch)
     end
+
+    def platform_options
+      if local_arch
+        [ "--platform", "linux/#{local_arch}" ]
+      else
+        [ "--platform", "linux/amd64,linux/arm64" ]
+      end
+    end
 end

lib/kamal/commands/builder/native/cached.rb

@@ -1,25 +0,0 @@
-class Kamal::Commands::Builder::Native::Cached < Kamal::Commands::Builder::Native
-  def create
-    docker :buildx, :create, "--name", builder_name, "--use", "--driver=docker-container"
-  end
-
-  def remove
-    docker :buildx, :rm, builder_name
-  end
-
-  def push
-    docker :buildx, :build,
-      "--push",
-      *build_options,
-      build_context
-  end
-
-  def context_hosts
-    docker :buildx, :inspect, builder_name, "> /dev/null"
-  end
-
-  private
-    def builder_name
-      "kamal-#{config.service}-native-cached"
-    end
-end