build: support for saving local state by build ref

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>
Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

build/build.go

@@ -25,6 +25,7 @@ import (
 	"github.com/containerd/containerd/platforms"
 	"github.com/docker/buildx/builder"
 	"github.com/docker/buildx/driver"
+	"github.com/docker/buildx/localstate"
 	"github.com/docker/buildx/util/dockerutil"
 	"github.com/docker/buildx/util/imagetools"
 	"github.com/docker/buildx/util/progress"
@@ -650,6 +651,12 @@ func toSolveOpt(ctx context.Context, node builder.Node, multiDriver bool, opt Op
 		so.FrontendAttrs["ulimit"] = ulimits
 	}
 
+	// remember local state like directory path that is not sent to buildkit
+	so.Ref = identity.NewID()
+	if err := saveLocalState(so, opt, node, configDir); err != nil {
+		return nil, nil, err
+	}
+
 	return &so, releaseF, nil
 }
 
@@ -1612,3 +1619,40 @@ func noPrintFunc(opt map[string]Options) bool {
 	}
 	return true
 }
+
+func saveLocalState(so client.SolveOpt, opt Options, node builder.Node, configDir string) error {
+	var err error
+
+	if so.Ref == "" {
+		return nil
+	}
+
+	lp := opt.Inputs.ContextPath
+	dp := opt.Inputs.DockerfilePath
+	if lp != "" || dp != "" {
+		if lp != "" {
+			lp, err = filepath.Abs(lp)
+			if err != nil {
+				return err
+			}
+		}
+		if dp != "" {
+			dp, err = filepath.Abs(dp)
+			if err != nil {
+				return err
+			}
+		}
+		ls, err := localstate.New(configDir)
+		if err != nil {
+			return err
+		}
+		if err := ls.SaveRef(node.Builder, node.Name, so.Ref, localstate.State{
+			LocalPath:      lp,
+			DockerfilePath: dp,
+		}); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}