Builder default shell

Signed-off-by: John Howard <jhoward@microsoft.com>

rewritten from github.com/moby/moby b18ae8c9ccc2eb6cf8aa947f25eb6f1d20089776

frontend/dockerfile/command/command.go

@@ -3,42 +3,44 @@ package command
 
 // Define constants for the command strings
 const (
+	Add         = "add"
+	Arg         = "arg"
+	Cmd         = "cmd"
+	Copy        = "copy"
+	Entrypoint  = "entrypoint"
 	Env         = "env"
+	Expose      = "expose"
+	From        = "from"
+	Healthcheck = "healthcheck"
 	Label       = "label"
 	Maintainer  = "maintainer"
-	Add         = "add"
-	Copy        = "copy"
-	From        = "from"
 	Onbuild     = "onbuild"
-	Workdir     = "workdir"
 	Run         = "run"
-	Cmd         = "cmd"
-	Entrypoint  = "entrypoint"
-	Expose      = "expose"
-	Volume      = "volume"
-	User        = "user"
+	Shell       = "shell"
 	StopSignal  = "stopsignal"
-	Arg         = "arg"
-	Healthcheck = "healthcheck"
+	User        = "user"
+	Volume      = "volume"
+	Workdir     = "workdir"
 )
 
 // Commands is list of all Dockerfile commands
 var Commands = map[string]struct{}{
+	Add:         {},
+	Arg:         {},
+	Cmd:         {},
+	Copy:        {},
+	Entrypoint:  {},
 	Env:         {},
+	Expose:      {},
+	From:        {},
+	Healthcheck: {},
 	Label:       {},
 	Maintainer:  {},
-	Add:         {},
-	Copy:        {},
-	From:        {},
 	Onbuild:     {},
-	Workdir:     {},
 	Run:         {},
-	Cmd:         {},
-	Entrypoint:  {},
-	Expose:      {},
-	Volume:      {},
-	User:        {},
+	Shell:       {},
 	StopSignal:  {},
-	Arg:         {},
-	Healthcheck: {},
+	User:        {},
+	Volume:      {},
+	Workdir:     {},
 }

frontend/dockerfile/parser/parser.go

@@ -67,23 +67,24 @@ func init() {
 	// functions. Errors are propagated up by Parse() and the resulting AST can
 	// be incorporated directly into the existing AST as a next.
 	dispatch = map[string]func(string) (*Node, map[string]bool, error){
-		command.User:        parseString,
-		command.Onbuild:     parseSubCommand,
-		command.Workdir:     parseString,
+		command.Add:         parseMaybeJSONToList,
+		command.Arg:         parseNameOrNameVal,
+		command.Cmd:         parseMaybeJSON,
+		command.Copy:        parseMaybeJSONToList,
+		command.Entrypoint:  parseMaybeJSON,
 		command.Env:         parseEnv,
+		command.Expose:      parseStringsWhitespaceDelimited,
+		command.From:        parseString,
+		command.Healthcheck: parseHealthConfig,
 		command.Label:       parseLabel,
 		command.Maintainer:  parseString,
-		command.From:        parseString,
-		command.Add:         parseMaybeJSONToList,
-		command.Copy:        parseMaybeJSONToList,
+		command.Onbuild:     parseSubCommand,
 		command.Run:         parseMaybeJSON,
-		command.Cmd:         parseMaybeJSON,
-		command.Entrypoint:  parseMaybeJSON,
-		command.Expose:      parseStringsWhitespaceDelimited,
-		command.Volume:      parseMaybeJSONToList,
+		command.Shell:       parseMaybeJSON,
 		command.StopSignal:  parseString,
-		command.Arg:         parseNameOrNameVal,
-		command.Healthcheck: parseHealthConfig,
+		command.User:        parseString,
+		command.Volume:      parseMaybeJSONToList,
+		command.Workdir:     parseString,
 	}
 }