Introduce a "build dev" command

lib/kamal/cli/build.rb

@@ -5,11 +5,12 @@ class BuildError < StandardError; end
 
   desc "deliver", "Build app and push app image to registry then pull image on servers"
   def deliver
-    push
-    pull
+    invoke :push
+    invoke :pull
   end
 
   desc "push", "Build and push app image to registry"
+  option :output, type: :string, default: "registry", banner: "export_type", desc: "Exported type for the build result, and may be any exported type supported by 'buildx --output'."
   def push
     cli = self
 
@@ -49,7 +50,7 @@ def push
         end
 
         # Get the command here to ensure the Dir.chdir doesn't interfere with it
-        push = KAMAL.builder.push
+        push = KAMAL.builder.push(cli.options[:output])
 
         KAMAL.with_verbosity(:debug) do
           Dir.chdir(KAMAL.config.builder.build_directory) { execute *push }
@@ -108,6 +109,41 @@ def details
     end
   end
 
+  desc "dev", "Build using the working directory, tag it as dirty, and push to local image store."
+  option :output, type: :string, default: "docker", banner: "export_type", desc: "Exported type for the build result, and may be any exported type supported by 'buildx --output'."
+  def dev
+    cli = self
+
+    ensure_docker_installed
+
+    docker_included_files = Set.new(Kamal::Docker.included_files)
+    git_uncommitted_files = Set.new(Kamal::Git.uncommitted_files)
+    git_untracked_files = Set.new(Kamal::Git.untracked_files)
+
+    docker_uncommitted_files = docker_included_files & git_uncommitted_files
+    if docker_uncommitted_files.any?
+      say "WARNING: Files with uncommitted changes will be present in the dev container:", :yellow
+      docker_uncommitted_files.sort.each { |f| say "  #{f}", :yellow }
+      say
+    end
+
+    docker_untracked_files = docker_included_files & git_untracked_files
+    if docker_untracked_files.any?
+      say "WARNING: Untracked files will be present in the dev container:", :yellow
+      docker_untracked_files.sort.each { |f| say "  #{f}", :yellow }
+      say
+    end
+
+    with_env(KAMAL.config.builder.secrets) do
+      run_locally do
+        build = KAMAL.builder.push(cli.options[:output], tag_as_dirty: true)
+        KAMAL.with_verbosity(:debug) do
+          execute(*build)
+        end
+      end
+    end
+  end
+
   private
     def connect_to_remote_host(remote_host)
       remote_uri = URI.parse(remote_host)

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, :inspect_builder, :validate_image, :first_mirror, to: :target
+  delegate :create, :remove, :dev, :push, :clean, :pull, :info, :inspect_builder, :validate_image, :first_mirror, to: :target
   delegate :local?, :remote?, :cloud?, to: "config.builder"
 
   include Clone

lib/kamal/commands/builder/base.rb

@@ -13,11 +13,12 @@ def clean
     docker :image, :rm, "--force", config.absolute_image
   end
 
-  def push
+  def push(export_action = "registry", tag_as_dirty: false)
     docker :buildx, :build,
-      "--push",
+      "--output=type=#{export_action}",
       *platform_options(arches),
       *([ "--builder", builder_name ] unless docker_driver?),
+      *build_tag_options(tag_as_dirty: tag_as_dirty),
       *build_options,
       build_context
   end
@@ -37,7 +38,7 @@ def inspect_builder
   end
 
   def build_options
-    [ *build_tags, *build_cache, *build_labels, *build_args, *build_secrets, *build_dockerfile, *build_target, *build_ssh, *builder_provenance, *builder_sbom ]
+    [ *build_cache, *build_labels, *build_args, *build_secrets, *build_dockerfile, *build_target, *build_ssh, *builder_provenance, *builder_sbom ]
   end
 
   def build_context
@@ -58,8 +59,14 @@ def first_mirror
   end
 
   private
-    def build_tags
-      [ "-t", config.absolute_image, "-t", config.latest_image ]
+    def build_tag_names(tag_as_dirty: false)
+      tag_names = [ config.absolute_image, config.latest_image ]
+      tag_names.map! { |t| "#{t}-dirty" } if tag_as_dirty
+      tag_names
+    end
+
+    def build_tag_options(tag_as_dirty: false)
+      build_tag_names(tag_as_dirty: tag_as_dirty).flat_map { |name| [ "-t", name ] }
     end
 
     def build_cache

lib/kamal/docker.rb

@@ -0,0 +1,30 @@
+require "tempfile"
+require "open3"
+
+module Kamal::Docker
+  extend self
+  BUILD_CHECK_TAG = "kamal-local-build-check"
+
+  def included_files
+    Tempfile.create do |dockerfile|
+      dockerfile.write(<<~DOCKERFILE)
+        FROM busybox
+        COPY . app
+        WORKDIR app
+        CMD find . -type f | sed "s|^\./||"
+      DOCKERFILE
+      dockerfile.close
+
+      cmd = "docker buildx build -t=#{BUILD_CHECK_TAG} -f=#{dockerfile.path} ."
+      system(cmd) || raise("failed to build check image")
+    end
+
+    cmd = "docker run --rm #{BUILD_CHECK_TAG}"
+    out, err, status = Open3.capture3(cmd)
+    unless status
+      raise "failed to run check image:\n#{err}"
+    end
+
+    out.lines.map(&:strip)
+  end
+end

lib/kamal/git.rb

@@ -24,4 +24,14 @@ def uncommitted_changes
   def root
     `git rev-parse --show-toplevel`.strip
   end
+
+  # returns an array of relative path names of files with uncommitted changes
+  def uncommitted_files
+    `git ls-files --modified`.lines.map(&:strip)
+  end
+
+  # returns an array of relative path names of untracked files, including gitignored files
+  def untracked_files
+    `git ls-files --others`.lines.map(&:strip)
+  end
 end

test/cli/build_test.rb

@@ -26,7 +26,30 @@ class CliBuildTest < CliTestCase
         assert_match /Cloning repo into build directory/, output
         assert_match /git -C #{Dir.tmpdir}\/kamal-clones\/app-#{pwd_sha} clone #{Dir.pwd}/, output
         assert_match /docker --version && docker buildx version/, output
-        assert_match /docker buildx build --push --platform linux\/amd64 --builder kamal-local-docker-container -t dhh\/app:999 -t dhh\/app:latest --label service="app" --file Dockerfile \. as .*@localhost/, output
+        assert_match /docker buildx build --output=type=registry --platform linux\/amd64 --builder kamal-local-docker-container -t dhh\/app:999 -t dhh\/app:latest --label service="app" --file Dockerfile \. as .*@localhost/, output
+      end
+    end
+  end
+
+  test "push --output=docker" do
+    with_build_directory do |build_directory|
+      Kamal::Commands::Hook.any_instance.stubs(:hook_exists?).returns(true)
+      hook_variables = { version: 999, service_version: "app@999", hosts: "1.1.1.1,1.1.1.2,1.1.1.3,1.1.1.4", command: "build", subcommand: "push" }
+
+      SSHKit::Backend::Abstract.any_instance.expects(:capture_with_info)
+        .with(:git, "-C", anything, :"rev-parse", :HEAD)
+        .returns(Kamal::Git.revision)
+
+      SSHKit::Backend::Abstract.any_instance.expects(:capture_with_info)
+        .with(:git, "-C", anything, :status, "--porcelain")
+        .returns("")
+
+      run_command("push", "--output=docker", "--verbose").tap do |output|
+        assert_hook_ran "pre-build", output, **hook_variables
+        assert_match /Cloning repo into build directory/, output
+        assert_match /git -C #{Dir.tmpdir}\/kamal-clones\/app-#{pwd_sha} clone #{Dir.pwd}/, output
+        assert_match /docker --version && docker buildx version/, output
+        assert_match /docker buildx build --output=type=docker --platform linux\/amd64 --builder kamal-local-docker-container -t dhh\/app:999 -t dhh\/app:latest --label service="app" --file Dockerfile \. as .*@localhost/, output
       end
     end
   end
@@ -49,7 +72,7 @@ class CliBuildTest < CliTestCase
       SSHKit::Backend::Abstract.any_instance.expects(:execute).with(:git, "-C", build_directory, :submodule, :update, "--init")
 
       SSHKit::Backend::Abstract.any_instance.expects(:execute)
-        .with(:docker, :buildx, :build, "--push", "--platform", "linux/amd64", "--builder", "kamal-local-docker-container", "-t", "dhh/app:999", "-t", "dhh/app:latest", "--label", "service=\"app\"", "--file", "Dockerfile", ".")
+        .with(:docker, :buildx, :build, "--output=type=registry", "--platform", "linux/amd64", "--builder", "kamal-local-docker-container", "-t", "dhh/app:999", "-t", "dhh/app:latest", "--label", "service=\"app\"", "--file", "Dockerfile", ".")
 
       SSHKit::Backend::Abstract.any_instance.expects(:capture_with_info)
         .with(:git, "-C", anything, :"rev-parse", :HEAD)
@@ -74,7 +97,7 @@ class CliBuildTest < CliTestCase
       assert_no_match /Cloning repo into build directory/, output
       assert_hook_ran "pre-build", output, **hook_variables
       assert_match /docker --version && docker buildx version/, output
-      assert_match /docker buildx build --push --platform linux\/amd64 --builder kamal-local-docker-container -t dhh\/app:999 -t dhh\/app:latest --label service="app" --file Dockerfile . as .*@localhost/, output
+      assert_match /docker buildx build --output=type=registry --platform linux\/amd64 --builder kamal-local-docker-container -t dhh\/app:999 -t dhh\/app:latest --label service="app" --file Dockerfile . as .*@localhost/, output
     end
   end
 
@@ -140,7 +163,7 @@ class CliBuildTest < CliTestCase
         .returns("")
 
       SSHKit::Backend::Abstract.any_instance.expects(:execute)
-        .with(:docker, :buildx, :build, "--push", "--platform", "linux/amd64", "--builder", "kamal-local-docker-container", "-t", "dhh/app:999", "-t", "dhh/app:latest", "--label", "service=\"app\"", "--file", "Dockerfile", ".")
+        .with(:docker, :buildx, :build, "--output=type=registry", "--platform", "linux/amd64", "--builder", "kamal-local-docker-container", "-t", "dhh/app:999", "-t", "dhh/app:latest", "--label", "service=\"app\"", "--file", "Dockerfile", ".")
 
       run_command("push").tap do |output|
         assert_match /WARN Missing compatible builder, so creating a new one first/, output
@@ -275,6 +298,30 @@ class CliBuildTest < CliTestCase
     end
   end
 
+  test "dev" do
+    with_build_directory do |build_directory|
+      Kamal::Commands::Hook.any_instance.stubs(:hook_exists?).returns(true)
+
+      run_command("dev", "--verbose").tap do |output|
+        assert_no_match(/Cloning repo into build directory/, output)
+        assert_match(/docker --version && docker buildx version/, output)
+        assert_match(/docker buildx build --output=type=docker --platform linux\/amd64 --builder kamal-local-docker-container -t dhh\/app:999-dirty -t dhh\/app:latest-dirty --label service="app" --file Dockerfile \. as .*@localhost/, output)
+      end
+    end
+  end
+
+  test "dev --output=local" do
+    with_build_directory do |build_directory|
+      Kamal::Commands::Hook.any_instance.stubs(:hook_exists?).returns(true)
+
+      run_command("dev", "--output=local", "--verbose").tap do |output|
+        assert_no_match(/Cloning repo into build directory/, output)
+        assert_match(/docker --version && docker buildx version/, output)
+        assert_match(/docker buildx build --output=type=local --platform linux\/amd64 --builder kamal-local-docker-container -t dhh\/app:999-dirty -t dhh\/app:latest-dirty --label service="app" --file Dockerfile \. as .*@localhost/, output)
+      end
+    end
+  end
+
   private
     def run_command(*command, fixture: :with_accessories)
       stdouted { Kamal::Cli::Build.start([ *command, "-c", "test/fixtures/deploy_#{fixture}.yml" ]) }