Build from within a git clone by default

Docker does not respect the .dockerignore file when building from a tar.

Instead by default we'll make a local clone into a tmp directory and
build from there. Subsequent builds will reset the clone to match the
checkout.

Compared to building directly in the repo, we'll have reproducible
builds.

Compared to using a git archive:
1. .dockerignore is respected
2. We'll have faster builds - docker can be smarter about caching the
build context on subsequent builds from a directory

To build from the repo directly, set the build context to "." in the
config.

If there are uncommitted changes, we'll warn about them either being
included or ignored depending on whether we build from the clone.

lib/kamal/cli/build.rb

@@ -19,21 +19,34 @@ class Kamal::Cli::Build < Kamal::Cli::Base
       verify_local_dependencies
       run_hook "pre-build"
 
-      if (uncommitted_changes = Kamal::Git.uncommitted_changes).present?
-        say "The following paths have uncommitted changes:\n #{uncommitted_changes}", :yellow
+      uncommitted_changes = Kamal::Git.uncommitted_changes
+
+      if KAMAL.config.builder.git_clone?
+        if uncommitted_changes.present?
+          say "Building from a local git clone, so ignoring these uncommitted changes:\n #{uncommitted_changes}", :yellow
+        end
+
+        prepare_clone
+      elsif uncommitted_changes.present?
+        say "Building with uncommitted changes:\n #{uncommitted_changes}", :yellow
       end
 
+      # Get the command here to ensure the Dir.chdir doesn't interfere with it
+      push = KAMAL.builder.push
+
       run_locally do
         begin
           KAMAL.with_verbosity(:debug) do
-            execute *KAMAL.builder.push
+            Dir.chdir(KAMAL.config.builder.build_directory) { execute *push }
           end
         rescue SSHKit::Command::Failed => e
           if e.message =~ /(no builder)|(no such file or directory)/
             warn "Missing compatible builder, so creating a new one first"
 
             if cli.create
-              KAMAL.with_verbosity(:debug) { execute *KAMAL.builder.push }
+              KAMAL.with_verbosity(:debug) do
+                Dir.chdir(KAMAL.config.builder.build_directory) { execute *push }
+              end
             end
           else
             raise
@@ -120,4 +133,23 @@ class Kamal::Cli::Build < Kamal::Cli::Base
         end
       end
     end
+
+    def prepare_clone
+      run_locally do
+        begin
+          info "Cloning repo into build directory `#{KAMAL.config.builder.build_directory}`..."
+
+          execute *KAMAL.builder.create_clone_directory
+          execute *KAMAL.builder.clone
+        rescue SSHKit::Command::Failed => e
+          if e.message =~ /already exists and is not an empty directory/
+            info "Resetting local clone as `#{KAMAL.config.builder.build_directory}` already exists..."
+
+            KAMAL.builder.clone_reset_steps.each { |step| execute *step }
+          else
+            raise
+          end
+        end
+      end
+    end
 end

lib/kamal/commands/base.rb

@@ -78,8 +78,8 @@ module Kamal::Commands
         args.compact.unshift :docker
       end
 
-      def git(*args)
-        args.compact.unshift :git
+      def git(*args, path: nil)
+        [ :git, *([ "-C", path ] if path), *args.compact ]
       end
 
       def tags(**details)

lib/kamal/commands/builder.rb

@@ -2,6 +2,7 @@ require "active_support/core_ext/string/filters"
 
 class Kamal::Commands::Builder < Kamal::Commands::Base
   delegate :create, :remove, :push, :clean, :pull, :info, :validate_image, to: :target
+  delegate :clone_directory, :build_directory, to: :"config.builder"
 
   def name
     target.class.to_s.remove("Kamal::Commands::Builder::").underscore.inquiry
@@ -53,6 +54,23 @@ class Kamal::Commands::Builder < Kamal::Commands::Base
     end
   end
 
+  def create_clone_directory
+    make_directory clone_directory
+  end
+
+  def clone
+    git :clone, Kamal::Git.root, path: clone_directory
+  end
+
+  def clone_reset_steps
+    [
+      git(:remote, "set-url", :origin, Kamal::Git.root, path: build_directory),
+      git(:fetch, :origin, path: build_directory),
+      git(:reset, "--hard", Kamal::Git.revision, path: build_directory),
+      git(:clean, "-fdx", path: build_directory)
+    ]
+  end
+
   private
     def ensure_local_docker_installed
       docker "--version"

lib/kamal/commands/builder/base.rb

@@ -3,7 +3,7 @@ class Kamal::Commands::Builder::Base < Kamal::Commands::Base
   class BuilderError < StandardError; end
 
   delegate :argumentize, to: Kamal::Utils
-  delegate :args, :secrets, :dockerfile, :target, :local_arch, :local_host, :remote_arch, :remote_host, :cache_from, :cache_to, :ssh, :git_archive?, to: :builder_config
+  delegate :args, :secrets, :dockerfile, :target, :local_arch, :local_host, :remote_arch, :remote_host, :cache_from, :cache_to, :ssh, to: :builder_config
 
   def clean
     docker :image, :rm, "--force", config.absolute_image
@@ -13,16 +13,6 @@ class Kamal::Commands::Builder::Base < Kamal::Commands::Base
     docker :pull, config.absolute_image
   end
 
-  def push
-    if git_archive?
-      pipe \
-        git(:archive, "--format=tar", :HEAD),
-        build_and_push
-    else
-      build_and_push
-    end
-  end
-
   def build_options
     [ *build_tags, *build_cache, *build_labels, *build_args, *build_secrets, *build_dockerfile, *build_target, *build_ssh ]
   end

lib/kamal/commands/builder/multiarch.rb

@@ -13,6 +13,15 @@ class Kamal::Commands::Builder::Multiarch < Kamal::Commands::Builder::Base
       docker(:buildx, :ls)
   end
 
+  def push
+    docker :buildx, :build,
+      "--push",
+      "--platform", platform_names,
+      "--builder", builder_name,
+      *build_options,
+      build_context
+  end
+
   private
     def builder_name
       "kamal-#{config.service}-multiarch"
@@ -25,13 +34,4 @@ class Kamal::Commands::Builder::Multiarch < Kamal::Commands::Builder::Base
         "linux/amd64,linux/arm64"
       end
     end
-
-    def build_and_push
-      docker :buildx, :build,
-        "--push",
-        "--platform", platform_names,
-        "--builder", builder_name,
-        *build_options,
-        build_context
-    end
 end

lib/kamal/commands/builder/native.rb

@@ -11,11 +11,10 @@ class Kamal::Commands::Builder::Native < Kamal::Commands::Builder::Base
     # No-op on native
   end
 
-  private
-    def build_and_push
-      combine \
-        docker(:build, *build_options, build_context),
-        docker(:push, config.absolute_image),
-        docker(:push, config.latest_image)
-    end
+  def push
+    combine \
+      docker(:build, *build_options, build_context),
+      docker(:push, config.absolute_image),
+      docker(:push, config.latest_image)
+  end
 end

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

@@ -7,11 +7,10 @@ class Kamal::Commands::Builder::Native::Cached < Kamal::Commands::Builder::Nativ
     docker :buildx, :rm, builder_name
   end
 
-  private
-    def build_and_push
-      docker :buildx, :build,
-        "--push",
-        *build_options,
-        build_context
-    end
+  def push
+    docker :buildx, :build,
+      "--push",
+      *build_options,
+      build_context
+  end
 end

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

@@ -17,6 +17,15 @@ class Kamal::Commands::Builder::Native::Remote < Kamal::Commands::Builder::Nativ
       docker(:buildx, :ls)
   end
 
+  def push
+    docker :buildx, :build,
+    "--push",
+    "--platform", platform,
+    "--builder", builder_name,
+    *build_options,
+    build_context
+  end
+
 
   private
     def builder_name
@@ -47,13 +56,4 @@ class Kamal::Commands::Builder::Native::Remote < Kamal::Commands::Builder::Nativ
     def remove_buildx
       docker :buildx, :rm, builder_name
     end
-
-    def build_and_push
-      docker :buildx, :build,
-      "--push",
-      "--platform", platform,
-      "--builder", builder_name,
-      *build_options,
-      build_context
-    end
 end

lib/kamal/configuration.rb

@@ -336,7 +336,7 @@ class Kamal::Configuration
     def git_version
       @git_version ||=
         if Kamal::Git.used?
-          if Kamal::Git.uncommitted_changes.present? && !builder.git_archive?
+          if Kamal::Git.uncommitted_changes.present? && !builder.git_clone?
             uncommitted_suffix = "_uncommitted_#{SecureRandom.hex(8)}"
           end
           [ Kamal::Git.revision, uncommitted_suffix ].compact.join

lib/kamal/configuration/builder.rb

@@ -3,6 +3,8 @@ class Kamal::Configuration::Builder
     @options = config.raw_config.builder || {}
     @image = config.image
     @server = config.registry["server"]
+    @service = config.service
+    @destination = config.destination
 
     valid?
   end
@@ -44,7 +46,7 @@ class Kamal::Configuration::Builder
   end
 
   def context
-    @options["context"] || (git_archive? ? "-" : ".")
+    @options["context"] || "."
   end
 
   def local_arch
@@ -89,10 +91,23 @@ class Kamal::Configuration::Builder
     @options["ssh"]
   end
 
-  def git_archive?
+  def git_clone?
     Kamal::Git.used? && @options["context"].nil?
   end
 
+  def clone_directory
+    @clone_directory ||= File.join Dir.tmpdir, "kamal-clones", [ @service, @destination, pwd_sha ].compact.join("-")
+  end
+
+  def build_directory
+    @build_directory ||=
+      if git_clone?
+        File.join clone_directory, repo_basename, repo_relative_pwd
+      else
+        "."
+      end
+  end
+
   private
     def valid?
       if @options["cache"] && @options["cache"]["type"]
@@ -123,4 +138,16 @@ class Kamal::Configuration::Builder
     def cache_to_config_for_registry
       [ "type=registry", @options["cache"]&.fetch("options", nil), "ref=#{cache_image_ref}" ].compact.join(",")
     end
+
+    def repo_basename
+      File.basename(Kamal::Git.root)
+    end
+
+    def repo_relative_pwd
+      Dir.pwd.delete_prefix(Kamal::Git.root)
+    end
+
+    def pwd_sha
+      Digest::SHA256.hexdigest(Dir.pwd)[0..12]
+    end
 end

lib/kamal/git.rb

@@ -16,4 +16,8 @@ module Kamal::Git
   def uncommitted_changes
     `git status --porcelain`.strip
   end
+
+  def root
+    `git rev-parse --show-toplevel`.strip
+  end
 end