Build and clean remote builders correctly

Check that the builder and context match what we expect, and if not
remove and re-create them.

lib/kamal/cli/build.rb

@@ -32,10 +32,15 @@ class Kamal::Cli::Build < Kamal::Cli::Base
 
     run_locally do
       begin
-        execute *KAMAL.builder.buildx_inspect
+        execute *KAMAL.builder.inspect_builder
       rescue SSHKit::Command::Failed => e
-        if e.message =~ /(context not found|no builder|does not exist)/
+        if e.message =~ /(context not found|no builder|no compatible builder|does not exist)/
           warn "Missing compatible builder, so creating a new one first"
+          begin
+            cli.remove
+          rescue SSHKit::Command::Failed
+            raise unless e.message =~ /(context not found|no builder|does not exist)/
+          end
           cli.create
         else
           raise

lib/kamal/commands/base.rb

@@ -81,6 +81,10 @@ module Kamal::Commands
         [ :git, *([ "-C", path ] if path), *args.compact ]
       end
 
+      def grep(*args)
+        args.compact.unshift :grep
+      end
+
       def tags(**details)
         Kamal::Tags.from_config(config, **details)
       end

lib/kamal/commands/builder.rb

@@ -1,7 +1,7 @@
 require "active_support/core_ext/string/filters"
 
 class Kamal::Commands::Builder < Kamal::Commands::Base
-  delegate :create, :remove, :push, :clean, :pull, :info, :buildx_inspect, :validate_image, :first_mirror, to: :target
+  delegate :create, :remove, :push, :clean, :pull, :info, :inspect_builder, :validate_image, :first_mirror, to: :target
   delegate :local?, :remote?, to: "config.builder"
 
   include Clone

lib/kamal/commands/builder/base.rb

@@ -32,7 +32,7 @@ class Kamal::Commands::Builder::Base < Kamal::Commands::Base
       docker(:buildx, :ls)
   end
 
-  def buildx_inspect
+  def inspect_builder
     docker :buildx, :inspect, builder_name unless docker_driver?
   end
 
@@ -101,10 +101,6 @@ class Kamal::Commands::Builder::Base < Kamal::Commands::Base
       config.builder
     end
 
-    def context_host(builder_name)
-      docker :context, :inspect, builder_name, "--format", ENDPOINT_DOCKER_HOST_INSPECT
-    end
-
     def platform_options(arches)
       argumentize "--platform", arches.map { |arch| "linux/#{arch}" }.join(",") if arches.any?
     end

lib/kamal/commands/builder/hybrid.rb

@@ -16,6 +16,6 @@ class Kamal::Commands::Builder::Hybrid < Kamal::Commands::Builder::Remote
     end
 
     def append_remote_buildx
-      docker :buildx, :create, *platform_options(remote_arches), "--append", "--name", builder_name, builder_name
+      docker :buildx, :create, *platform_options(remote_arches), "--append", "--name", builder_name, remote_context_name
     end
 end

lib/kamal/commands/builder/remote.rb

@@ -17,21 +17,44 @@ class Kamal::Commands::Builder::Remote < Kamal::Commands::Builder::Base
       docker(:buildx, :ls)
   end
 
+  def inspect_builder
+    combine \
+      combine inspect_buildx, inspect_remote_context,
+      [ "(echo no compatible builder && exit 1)" ],
+      by: "||"
+  end
+
   private
     def builder_name
-      "kamal-remote-#{driver}-#{remote.gsub(/[^a-z0-9_-]/, "-")}"
+      "kamal-remote-#{remote.gsub(/[^a-z0-9_-]/, "-")}"
+    end
+
+    def remote_context_name
+      "#{builder_name}-context"
+    end
+
+    def inspect_buildx
+      pipe \
+        docker(:buildx, :inspect, builder_name),
+        grep("-q", "Endpoint:.*#{remote_context_name}")
+    end
+
+    def inspect_remote_context
+      pipe \
+        docker(:context, :inspect, remote_context_name, "--format", ENDPOINT_DOCKER_HOST_INSPECT),
+        grep("-xq", remote)
     end
 
     def create_remote_context
-      docker :context, :create, builder_name, "--description", "'#{builder_name} host'", "--docker", "'host=#{remote}'"
+      docker :context, :create, remote_context_name, "--description", "'#{builder_name} host'", "--docker", "'host=#{remote}'"
     end
 
     def remove_remote_context
-      docker :context, :rm, builder_name
+      docker :context, :rm, remote_context_name
     end
 
     def create_buildx
-      docker :buildx, :create, "--name", builder_name, builder_name
+      docker :buildx, :create, "--name", builder_name, remote_context_name
     end
 
     def remove_buildx

lib/kamal/commands/prune.rb

@@ -9,7 +9,7 @@ class Kamal::Commands::Prune < Kamal::Commands::Base
   def tagged_images
     pipe \
       docker(:image, :ls, *service_filter, "--format", "'{{.ID}} {{.Repository}}:{{.Tag}}'"),
-      "grep -v -w \"#{active_image_list}\"",
+      grep("-v -w \"#{active_image_list}\""),
       "while read image tag; do docker rmi $tag; done"
   end