ignore invalid Dockerfile instructions and do not consider "docker-version" a Dockerfile instruction

Signed-off-by: Tibor Vass <teabee89@gmail.com>

builder/evaluator.go

@@ -52,7 +52,6 @@ func init() {
 		"from":       from,
 		"onbuild":    onbuild,
 		"workdir":    workdir,
-		"docker-version": nullDispatch, // we don't care about docker-version
 		"run":        run,
 		"cmd":        cmd,
 		"entrypoint": entrypoint,

builder/parser/parser.go

@@ -48,7 +48,6 @@ func init() {
 		"workdir":    parseString,
 		"env":        parseEnv,
 		"maintainer": parseString,
-		"docker-version": parseString,
 		"from":       parseString,
 		"add":        parseStringsWhitespaceDelimited,
 		"copy":       parseStringsWhitespaceDelimited,

builder/parser/testfiles/docker/result

@@ -1,4 +1,4 @@
-(docker-version "0.6.1")
+(docker-version)
 (from "ubuntu:14.04")
 (maintainer "Tianon Gravi <admwiggin@gmail.com> (@tianon)")
 (run "apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -yq 	apt-utils 	aufs-tools 	automake 	btrfs-tools 	build-essential 	curl 	dpkg-sig 	git 	iptables 	libapparmor-dev 	libcap-dev 	libsqlite3-dev 	lxc=1.0* 	mercurial 	pandoc 	parallel 	reprepro 	ruby1.9.1 	ruby1.9.1-dev 	s3cmd=1.1.0* 	--no-install-recommends")

builder/parser/utils.go

@@ -1,9 +1,6 @@
 package parser
 
-import (
-	"fmt"
-	"strings"
-)
+import "strings"
 
 // QuoteString walks characters (after trimming), escapes any quotes and
 // escapes, then wraps the whole thing in quotes. Very useful for generating
@@ -52,11 +49,14 @@ func (node *Node) Dump() string {
 // performs the dispatch based on the two primal strings, cmd and args. Please
 // look at the dispatch table in parser.go to see how these dispatchers work.
 func fullDispatch(cmd, args string) (*Node, map[string]bool, error) {
-	if _, ok := dispatch[cmd]; !ok {
-		return nil, nil, fmt.Errorf("'%s' is not a valid dockerfile command", cmd)
+	fn := dispatch[cmd]
+
+	// Ignore invalid Dockerfile instructions
+	if fn == nil {
+		fn = parseIgnore
 	}
 
-	sexp, attrs, err := dispatch[cmd](args)
+	sexp, attrs, err := fn(args)
 	if err != nil {
 		return nil, nil, err
 	}