Stabilize dockerfile heredoc support

Signed-off-by: Justin Chadwell <me@jedevc.com>

.golangci.yml

@@ -7,7 +7,6 @@ run:
 
   build-tags:
     - dfrunsecurity
-    - dfheredoc
 
 linters:
   enable:

frontend/dockerfile/dockerfile_heredoc_test.go

@@ -1,6 +1,3 @@
-//go:build dfheredoc
-// +build dfheredoc
-
 package dockerfile
 
 import (

frontend/dockerfile/instructions/parse_heredoc_test.go

@@ -1,6 +1,3 @@
-//go:build dfheredoc
-// +build dfheredoc
-
 package instructions
 
 import (

frontend/dockerfile/parser/parser.go

@@ -130,8 +130,17 @@ var validDirectives = map[string]struct{}{
 }
 
 var (
-	heredocDirectives         map[string]bool // directives allowed to contain heredocs
-	heredocCompoundDirectives map[string]bool // directives allowed to contain directives containing heredocs
+	// Directives allowed to contain heredocs
+	heredocDirectives = map[string]bool{
+		command.Add:  true,
+		command.Copy: true,
+		command.Run:  true,
+	}
+
+	// Directives allowed to contain directives containing heredocs
+	heredocCompoundDirectives = map[string]bool{
+		command.Onbuild: true,
+	}
 )
 
 // directive is the structure used during a build run to hold the state of

frontend/dockerfile/parser/parser_heredoc.go

@@ -1,18 +0,0 @@
-//go:build dfheredoc
-// +build dfheredoc
-
-package parser
-
-import "github.com/moby/buildkit/frontend/dockerfile/command"
-
-func init() {
-	heredocDirectives = map[string]bool{
-		command.Add:  true,
-		command.Copy: true,
-		command.Run:  true,
-	}
-
-	heredocCompoundDirectives = map[string]bool{
-		command.Onbuild: true,
-	}
-}

frontend/dockerfile/parser/parser_heredoc_test.go

@@ -1,6 +1,3 @@
-//go:build dfheredoc
-// +build dfheredoc
-
 package parser
 
 import (

frontend/dockerfile/release/labs/tags

@@ -1 +1 @@
-dfrunsecurity dfheredoc
+dfrunsecurity