feat(docker): add buildpacks support (#2461)

* feat(docker): add buildpacks support

Signed-off-by: Erkan Zileli <erkanzileli@gmail.com>

* fix: move buildpacker imager code into own go file

Signed-off-by: Batuhan Apaydın <batuhan.apaydin@trendyol.com>

* fix: use docker imager push method for buildpack imager push

Signed-off-by: Batuhan Apaydın <batuhan.apaydin@trendyol.com>

* fix: return statement

Signed-off-by: Batuhan Apaydın <batuhan.apaydin@trendyol.com>

* move test into api_buildback_test

Signed-off-by: Furkan <furkan.turkal@trendyol.com>

* fix: use buildpacks instead of buildpack

Signed-off-by: Batuhan Apaydın <batuhan.apaydin@trendyol.com>

* fix(lint): fix lint issue

* fix(buildpacks): use cwd instead of root directory

* doc: add how to use a custom buildpack document

Signed-off-by: Erkan Zileli <erkan.zileli@trendyol.com>

* fix(doc): update docs as suggested

Co-authored-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

Co-authored-by: Batuhan Apaydın <batuhan.apaydin@trendyol.com>
Co-authored-by: Furkan <furkan.turkal@trendyol.com>
Co-authored-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

internal/pipe/docker/api_buildpack.go

@@ -0,0 +1,40 @@
+package docker
+
+import (
+	"context"
+	"fmt"
+	"strings"
+)
+
+type buildPackImager struct{}
+
+func (i buildPackImager) Push(ctx context.Context, image string, flags []string) error {
+	return dockerImager{}.Push(ctx, image, flags)
+}
+
+func (i buildPackImager) Build(ctx context.Context, root string, images, flags []string) error {
+	if err := runCommand(ctx, "", "pack", i.buildCommand(images, flags)...); err != nil {
+		return fmt.Errorf("failed to build %s: %w", images[0], err)
+	}
+	return nil
+}
+
+func (i buildPackImager) buildCommand(images, flags []string) []string {
+	base := []string{"build", images[0]}
+	for j := 1; j < len(images); j++ {
+		base = append(base, "-t", images[j])
+	}
+
+	builderConfigured := false
+	for _, flag := range flags {
+		if strings.HasPrefix(flag, "-B") || strings.HasPrefix(flag, "--builder") {
+			builderConfigured = true
+		}
+	}
+
+	if !builderConfigured {
+		flags = append(flags, "--builder=gcr.io/buildpacks/builder:v1")
+	}
+
+	return append(base, flags...)
+}

internal/pipe/docker/api_buildpack_test.go

@@ -0,0 +1,48 @@
+package docker
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestBuildCommandForBuildPack(t *testing.T) {
+	images := []string{"goreleaser/test_build_flag", "goreleaser/test_multiple_tags"}
+	tests := []struct {
+		name   string
+		flags  []string
+		expect []string
+	}{
+		{
+			name:   "no flags without builder",
+			flags:  []string{},
+			expect: []string{"build", images[0], "-t", images[1], "--builder=gcr.io/buildpacks/builder:v1"},
+		},
+		{
+			name:   "single flag without builder",
+			flags:  []string{"--clear-cache"},
+			expect: []string{"build", images[0], "-t", images[1], "--clear-cache", "--builder=gcr.io/buildpacks/builder:v1"},
+		},
+		{
+			name:   "multiple flags without builder",
+			flags:  []string{"--clear-cache", "--verbose"},
+			expect: []string{"build", images[0], "-t", images[1], "--clear-cache", "--verbose", "--builder=gcr.io/buildpacks/builder:v1"},
+		},
+		{
+			name:   "builder with --builder flag",
+			flags:  []string{"--builder=heroku/buildpacks:20"},
+			expect: []string{"build", images[0], "-t", images[1], "--builder=heroku/buildpacks:20"},
+		},
+		{
+			name:   "builder with -B flag",
+			flags:  []string{"-B=heroku/buildpacks:18"},
+			expect: []string{"build", images[0], "-t", images[1], "-B=heroku/buildpacks:18"},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			imager := buildPackImager{}
+			require.Equal(t, tt.expect, imager.buildCommand(images, tt.flags))
+		})
+	}
+}

internal/pipe/docker/api_docker.go

@@ -12,6 +12,7 @@ func init() {
 	registerImager(useBuildx, dockerImager{
 		buildx: true,
 	})
+	registerImager(useBuildPack, buildPackImager{})
 }
 
 type dockerManifester struct{}

internal/pipe/docker/docker.go

@@ -24,8 +24,9 @@ import (
 const (
 	dockerConfigExtra = "DockerConfig"
 
-	useBuildx = "buildx"
+	useBuildx    = "buildx"
-	useDocker = "docker"
+	useDocker    = "docker"
+	useBuildPack = "buildpacks"
 )
 
 // Pipe for docker.

internal/pipe/docker/docker_test.go

@@ -929,6 +929,9 @@ func TestRunPipe(t *testing.T) {
 
 	for name, docker := range table {
 		for imager := range imagers {
+			if imager == useBuildPack { // buildpack tests are different
+				continue
+			}
 			t.Run(name+" on "+imager, func(t *testing.T) {
 				folder := t.TempDir()
 				dist := filepath.Join(folder, "dist")

www/docs/customization/docker.md

@@ -86,7 +86,7 @@ dockers:
     dockerfile: Dockerfile
 
     # Set the "backend" for the Docker pipe.
-    # Valid options are: docker, buildx, podman
+    # Valid options are: docker, buildx, podman, buildpacks
     # podman is a GoReleaser Pro feature and is only available on Linux.
     # Defaults to docker.
     use: docker
@@ -255,3 +255,30 @@ Also worth noticing that currently Podman only works on Linux machines.
 
 !!! info
     The Podman backend is a [GoReleaser Pro feature](/pro/).
+
+## Buildpacks
+
+You can use [`buildpacks`](https://buildpacks.io) instead of `docker` by setting `use` to `buildpacks` on your config:
+
+```yaml
+# .goreleaser.yml
+dockers:
+  -
+    image_templates:
+    - "myuser/myimage"
+    use: buildpacks
+```
+
+Also, you can use a custom buildpack on `build_flag_templates` if you want. 
+By default, `gcr.io/buildpacks/builder:v1` will be used.
+
+```yaml
+# .goreleaser.yml
+dockers:
+  -
+    image_templates:
+    - "myuser/myimage"
+    use: buildpacks
+    build_flag_templates:
+    - "--builder=heroku/buildpacks:20"
+```