allow to use --only with post-processors

command/build_test.go

@@ -76,6 +76,7 @@ func TestBuildOnlyFileMultipleFlags(t *testing.T) {
 	args := []string{
 		"-only=chocolate",
 		"-only=cherry",
+		"-only=apple",
 		filepath.Join(testFixture("build-only"), "template.json"),
 	}
 
@@ -94,6 +95,9 @@ func TestBuildOnlyFileMultipleFlags(t *testing.T) {
 	if !fileExists("cherry.txt") {
 		t.Error("Expected to find cherry.txt")
 	}
+	if !fileExists("apple.txt") {
+		t.Error("Expected to find apple.txt")
+	}
 }
 
 func TestBuildExceptFileCommaFlags(t *testing.T) {

packer/core.go

@@ -182,6 +182,7 @@ func (c *Core) Build(n string) (Build, error) {
 		for _, rawP := range rawPs {
 			// If we skip, ignore
 			rawP.OnlyExcept.Except = append(rawP.OnlyExcept.Except, c.except...)
+			rawP.OnlyExcept.Only = append(rawP.OnlyExcept.Only, c.only...)
 			if rawP.OnlyExcept.Skip(rawName) {
 				continue
 			}