Redirect buildx build output to stdout

Docker buildx build outputs the build logs to stderr by default.
SSHKit displays stderr logs in red, which can suggest that an error has
occurred.

Redirect the output to stdout, so it shows in green. If there is an
error, the output will be repeated in red anyway.

Fixes: https://github.com/basecamp/kamal/issues/1356

lib/kamal/commands/builder/base.rb

@@ -20,7 +20,8 @@ class Kamal::Commands::Builder::Base < Kamal::Commands::Base
       *([ "--builder", builder_name ] unless docker_driver?),
       *build_tag_options(tag_as_dirty: tag_as_dirty),
       *build_options,
-      build_context
+      build_context,
+      "2>&1"
   end
 
   def pull

test/cli/build_test.rb

@@ -25,7 +25,7 @@ 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 --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
+        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 \. 2>&1 as .*@localhost/, output
       end
     end
   end
@@ -47,7 +47,7 @@ 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 --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
+        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 \. 2>&1 as .*@localhost/, output
       end
     end
   end
@@ -71,7 +71,7 @@ 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, "--output=type=registry", "--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", ".", "2>&1")
 
       SSHKit::Backend::Abstract.any_instance.expects(:capture_with_info)
         .with(:git, "-C", anything, :"rev-parse", :HEAD)
@@ -95,7 +95,7 @@ class CliBuildTest < CliTestCase
       assert_no_match /Cloning repo into build directory/, output
       assert_hook_ran "pre-build", output
       assert_match /docker --version && docker buildx version/, 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
+      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 . 2>&1 as .*@localhost/, output
     end
   end
 
@@ -165,7 +165,7 @@ class CliBuildTest < CliTestCase
         .returns("")
 
       SSHKit::Backend::Abstract.any_instance.expects(:execute)
-        .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", ".")
+        .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", ".", "2>&1")
 
       run_command("push").tap do |output|
         assert_match /WARN Missing compatible builder, so creating a new one first/, output
@@ -307,7 +307,7 @@ class CliBuildTest < CliTestCase
       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)
+        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 \. 2>&1 as .*@localhost/, output)
       end
     end
   end
@@ -319,7 +319,7 @@ class CliBuildTest < CliTestCase
       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)
+        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 \. 2>&1 as .*@localhost/, output)
       end
     end
   end

test/commands/builder_test.rb

@@ -9,7 +9,7 @@ class CommandsBuilderTest < ActiveSupport::TestCase
     builder = new_builder_command(builder: { "cache" => { "type" => "gha" } })
     assert_equal "local", builder.name
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile .",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile . 2>&1",
       builder.push.join(" ")
   end
 
@@ -17,7 +17,7 @@ class CommandsBuilderTest < ActiveSupport::TestCase
     builder = new_builder_command(builder: { "arch" => [ "amd64" ] })
     assert_equal "local", builder.name
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile .",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile . 2>&1",
       builder.push.join(" ")
   end
 
@@ -25,7 +25,7 @@ class CommandsBuilderTest < ActiveSupport::TestCase
     builder = new_builder_command(builder: { "cache" => { "type" => "gha" } })
     assert_equal "local", builder.name
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile .",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile . 2>&1",
       builder.push.join(" ")
   end
 
@@ -33,7 +33,7 @@ class CommandsBuilderTest < ActiveSupport::TestCase
     builder = new_builder_command(builder: { "arch" => [ "amd64", "arm64" ], "remote" => "ssh://app@127.0.0.1", "cache" => { "type" => "gha" } })
     assert_equal "hybrid", builder.name
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64,linux/arm64 --builder kamal-hybrid-docker-container-ssh---app-127-0-0-1 -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile .",
+      "docker buildx build --output=type=registry --platform linux/amd64,linux/arm64 --builder kamal-hybrid-docker-container-ssh---app-127-0-0-1 -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile . 2>&1",
       builder.push.join(" ")
   end
 
@@ -41,7 +41,7 @@ class CommandsBuilderTest < ActiveSupport::TestCase
     builder = new_builder_command(builder: { "arch" => [ "amd64", "arm64" ], "remote" => "ssh://app@127.0.0.1", "cache" => { "type" => "gha" }, "local" => false })
     assert_equal "remote", builder.name
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64,linux/arm64 --builder kamal-remote-ssh---app-127-0-0-1 -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile .",
+      "docker buildx build --output=type=registry --platform linux/amd64,linux/arm64 --builder kamal-remote-ssh---app-127-0-0-1 -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile . 2>&1",
       builder.push.join(" ")
   end
 
@@ -49,7 +49,7 @@ class CommandsBuilderTest < ActiveSupport::TestCase
     builder = new_builder_command(builder: { "arch" => [ "#{remote_arch}" ], "remote" => "ssh://app@host", "cache" => { "type" => "gha" } })
     assert_equal "remote", builder.name
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/#{remote_arch} --builder kamal-remote-ssh---app-host -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile .",
+      "docker buildx build --output=type=registry --platform linux/#{remote_arch} --builder kamal-remote-ssh---app-host -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile . 2>&1",
       builder.push.join(" ")
   end
 
@@ -57,7 +57,7 @@ class CommandsBuilderTest < ActiveSupport::TestCase
     builder = new_builder_command(builder: { "arch" => [ "#{local_arch}" ], "remote" => "ssh://app@host", "cache" => { "type" => "gha" } })
     assert_equal "local", builder.name
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/#{local_arch} --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile .",
+      "docker buildx build --output=type=registry --platform linux/#{local_arch} --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --cache-to type=gha --cache-from type=gha --label service=\"app\" --file Dockerfile . 2>&1",
       builder.push.join(" ")
   end
 
@@ -65,7 +65,7 @@ class CommandsBuilderTest < ActiveSupport::TestCase
     builder = new_builder_command(builder: { "arch" => [ "#{local_arch}" ], "driver" => "cloud docker-org-name/builder-name" })
     assert_equal "cloud", builder.name
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/#{local_arch} --builder cloud-docker-org-name-builder-name -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile .",
+      "docker buildx build --output=type=registry --platform linux/#{local_arch} --builder cloud-docker-org-name-builder-name -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile . 2>&1",
       builder.push.join(" ")
   end
 
@@ -112,14 +112,14 @@ class CommandsBuilderTest < ActiveSupport::TestCase
   test "build context" do
     builder = new_builder_command(builder: { "context" => ".." })
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile ..",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile .. 2>&1",
       builder.push.join(" ")
   end
 
   test "push with build args" do
     builder = new_builder_command(builder: { "args" => { "a" => 1, "b" => 2 } })
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --build-arg a=\"1\" --build-arg b=\"2\" --file Dockerfile .",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --build-arg a=\"1\" --build-arg b=\"2\" --file Dockerfile . 2>&1",
       builder.push.join(" ")
   end
 
@@ -128,7 +128,7 @@ class CommandsBuilderTest < ActiveSupport::TestCase
       FileUtils.touch("Dockerfile")
       builder = new_builder_command(builder: { "secrets" => [ "a", "b" ] })
       assert_equal \
-        "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --secret id=\"a\" --secret id=\"b\" --file Dockerfile .",
+        "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --secret id=\"a\" --secret id=\"b\" --file Dockerfile . 2>&1",
         builder.push.join(" ")
     end
   end
@@ -148,35 +148,35 @@ class CommandsBuilderTest < ActiveSupport::TestCase
   test "context build" do
     builder = new_builder_command(builder: { "context" => "./foo" })
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile ./foo",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile ./foo 2>&1",
       builder.push.join(" ")
   end
 
   test "push with provenance" do
     builder = new_builder_command(builder: { "provenance" => "mode=max" })
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile --provenance mode=max .",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile --provenance mode=max . 2>&1",
       builder.push.join(" ")
   end
 
   test "push with provenance false" do
     builder = new_builder_command(builder: { "provenance" => false })
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile --provenance false .",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile --provenance false . 2>&1",
       builder.push.join(" ")
   end
 
   test "push with sbom" do
     builder = new_builder_command(builder: { "sbom" => true })
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile --sbom true .",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile --sbom true . 2>&1",
       builder.push.join(" ")
   end
 
   test "push with sbom false" do
     builder = new_builder_command(builder: { "sbom" => false })
     assert_equal \
-      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile --sbom false .",
+      "docker buildx build --output=type=registry --platform linux/amd64 --builder kamal-local-docker-container -t dhh/app:123 -t dhh/app:latest --label service=\"app\" --file Dockerfile --sbom false . 2>&1",
       builder.push.join(" ")
   end