build: support --cache-from and --cache-to

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

README.md

@@ -603,8 +603,10 @@ Flags:
 - :whale: `--secret`: Secret file to expose to the build: id=mysecret,src=/local/secret
 - :whale: `--ssh`: SSH agent socket or keys to expose to the build (format: `default|<id>[=<socket>|<key>[,<key>]]`)
 - :whale: `-q, --quiet`: Suppress the build output and print image ID on success
+- :whale: `--cache-from=CACHE`: External cache sources (eg. user/app:cache, type=local,src=path/to/dir) (compatible with `docker buildx build`)
+- :whale: `--cache-to=CACHE`: Cache export destinations (eg. user/app:cache, type=local,dest=path/to/dir) (compatible with `docker buildx build`)
 
-Unimplemented `docker build` flags: `--add-host`, `--cache-from`, `--iidfile`, `--label`, `--network`, `--platform`, `--squash`
+Unimplemented `docker build` flags: `--add-host`, `--iidfile`, `--label`, `--network`, `--platform`, `--squash`
 
 ### :whale: nerdctl commit
 Create a new image from a container's changes

cmd/nerdctl/build.go

@@ -20,6 +20,7 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"strconv"
 	"strings"
 
 	"path/filepath"
@@ -89,6 +90,14 @@ var buildCommand = &cli.Command{
 			Aliases: []string{"q"},
 			Usage:   "Suppress the build output and print image ID on success",
 		},
+		&cli.StringSliceFlag{
+			Name:  "cache-from",
+			Usage: "External cache sources (eg. user/app:cache, type=local,src=path/to/dir)",
+		},
+		&cli.StringSliceFlag{
+			Name:  "cache-to",
+			Usage: "Cache export destinations (eg. user/app:cache, type=local,dest=path/to/dir)",
+		},
 	},
 }
 
@@ -192,6 +201,20 @@ func generateBuildctlArgs(clicontext *cli.Context) (string, []string, bool, erro
 
 	for _, ba := range strutil.DedupeStrSlice(clicontext.StringSlice("build-arg")) {
 		buildctlArgs = append(buildctlArgs, "--opt=build-arg:"+ba)
+
+		// Support `--build-arg BUILDKIT_INLINE_CACHE=1` for compatibility with `docker buildx build`
+		// https://github.com/docker/buildx/blob/v0.6.3/docs/reference/buildx_build.md#-export-build-cache-to-an-external-cache-destination---cache-to
+		if strings.HasPrefix(ba, "BUILDKIT_INLINE_CACHE=") {
+			bic := strings.TrimPrefix(ba, "BUILDKIT_INLINE_CACHE=")
+			bicParsed, err := strconv.ParseBool(bic)
+			if err == nil {
+				if bicParsed {
+					buildctlArgs = append(buildctlArgs, "--export-cache=type=inline")
+				}
+			} else {
+				logrus.WithError(err).Warnf("invalid BUILDKIT_INLINE_CACHE: %q", bic)
+			}
+		}
 	}
 
 	if clicontext.Bool("no-cache") {
@@ -206,5 +229,19 @@ func generateBuildctlArgs(clicontext *cli.Context) (string, []string, bool, erro
 		buildctlArgs = append(buildctlArgs, "--ssh="+s)
 	}
 
+	for _, s := range strutil.DedupeStrSlice(clicontext.StringSlice("cache-from")) {
+		if !strings.Contains(s, "type=") {
+			s = "type=registry,ref=" + s
+		}
+		buildctlArgs = append(buildctlArgs, "--import-cache="+s)
+	}
+
+	for _, s := range strutil.DedupeStrSlice(clicontext.StringSlice("cache-to")) {
+		if !strings.Contains(s, "type=") {
+			s = "type=registry,ref=" + s
+		}
+		buildctlArgs = append(buildctlArgs, "--export-cache="+s)
+	}
+
 	return buildctlBinary, buildctlArgs, needsLoading, nil
 }