bake: allow overriding no-cache and pull per target via --set

Signed-off-by: Tibor Vass <tibor@docker.com>

README.md

@@ -568,6 +568,9 @@ docker buildx bake --set foo*.args.mybuildarg=value	# overrides build arg for al
 docker buildx bake --set *.platform=linux/arm64		# overrides platform for all targets
 ```
 
+Complete list of overridable fields:
+	args, cache-from, cache-to, context, dockerfile, labels, no-cache, output, platform, pull, secrets, ssh, tags, target
+
 #### File definition
 
 In addition to compose files, bake supports a JSON and an equivalent HCL file format for defining build groups and targets.

bake/bake.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path"
+	"strconv"
 	"strings"
 
 	"github.com/docker/buildx/build"
@@ -194,6 +195,21 @@ func (c Config) newOverrides(v []string) (map[string]Target, error) {
 				t.Platforms = append(t.Platforms, parts[1])
 			case "output":
 				t.Outputs = append(t.Outputs, parts[1])
+			case "no-cache":
+				noCache, err := strconv.ParseBool(parts[1])
+				if err != nil {
+					return errors.Errorf("invalid value %s for boolean key no-cache", parts[1])
+				}
+				t.NoCache = noCache
+			case "pull":
+				pull, err := strconv.ParseBool(parts[1])
+				if err != nil {
+					return errors.Errorf("invalid value %s for boolean key pull", parts[1])
+				}
+				t.Pull = pull
+			/*
+			** IMPORTANT: if you add more overrides here, do not forget to update README.
+			*/
 			default:
 				return nil, errors.Errorf("unknown key: %s", keys[1])
 			}
@@ -283,6 +299,8 @@ type Target struct {
 	SSH        []string          `json:"ssh,omitempty" hcl:"ssh,omitempty"`
 	Platforms  []string          `json:"platforms,omitempty" hcl:"platforms,omitempty"`
 	Outputs    []string          `json:"output,omitempty" hcl:"output,omitempty"`
+	Pull       bool              `json:"pull,omitempty": hcl:"pull,omitempty"`
+	NoCache    bool              `json:"no-cache,omitempty": hcl:"no-cache,omitempty"`
 }
 
 func (t *Target) normalize() {

commands/build.go

@@ -62,9 +62,9 @@ type buildOptions struct {
 }
 
 type commonOptions struct {
-	noCache    bool
+	noCache    *bool
 	progress   string
-	pull       bool
+	pull       *bool
 	exportPush bool
 	exportLoad bool
 }