Allow specification of Label Name/Value pairs in image json content

Save "LABEL" field in Dockerfile into image content.

This will allow a user to save user data into an image, which
can later be retrieved using:

docker inspect IMAGEID

I have copied this from the "Comment" handling in docker images.

We want to be able to add Name/Value data to an image to describe the image,
and then be able to use other tools to look at this data, to be able to do
security checks based on this data.

We are thinking about adding version names,
Perhaps listing the content of the dockerfile.
Descriptions of where the code came from etc.

This LABEL field should also be allowed to be specified in the
docker import --change LABEL:Name=Value
docker commit --change LABEL:Name=Value

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

builder/command/command.go

@@ -3,6 +3,7 @@ package command
 
 const (
 	Env        = "env"
+	Label      = "label"
 	Maintainer = "maintainer"
 	Add        = "add"
 	Copy       = "copy"

builder/dispatchers.go

@@ -85,6 +85,37 @@ func maintainer(b *Builder, args []string, attributes map[string]bool, original
 	return b.commit("", b.Config.Cmd, fmt.Sprintf("MAINTAINER %s", b.maintainer))
 }
 
+// LABEL some json data describing the image
+//
+// Sets the Label variable foo to bar,
+//
+func label(b *Builder, args []string, attributes map[string]bool, original string) error {
+	if len(args) == 0 {
+		return fmt.Errorf("LABEL is missing arguments")
+	}
+	if len(args)%2 != 0 {
+		// should never get here, but just in case
+		return fmt.Errorf("Bad input to LABEL, too many args")
+	}
+
+	commitStr := "LABEL"
+
+	if b.Config.Labels == nil {
+		b.Config.Labels = map[string]string{}
+	}
+
+	for j := 0; j < len(args); j++ {
+		// name  ==> args[j]
+		// value ==> args[j+1]
+		newVar := args[j] + "=" + args[j+1] + ""
+		commitStr += " " + newVar
+
+		b.Config.Labels[args[j]] = args[j+1]
+		j++
+	}
+	return b.commit("", b.Config.Cmd, commitStr)
+}
+
 // ADD foo /path
 //
 // Add the file 'foo' to '/path'. Tarball and Remote URL (git, http) handling

builder/evaluator.go

@@ -62,6 +62,7 @@ var evaluateTable map[string]func(*Builder, []string, map[string]bool, string) e
 func init() {
 	evaluateTable = map[string]func(*Builder, []string, map[string]bool, string) error{
 		command.Env:        env,
+		command.Label:      label,
 		command.Maintainer: maintainer,
 		command.Add:        add,
 		command.Copy:       dispatchCopy, // copy() is a go builtin

builder/parser/line_parsers.go

@@ -44,10 +44,10 @@ func parseSubCommand(rest string) (*Node, map[string]bool, error) {
 
 // parse environment like statements. Note that this does *not* handle
 // variable interpolation, which will be handled in the evaluator.
-func parseEnv(rest string) (*Node, map[string]bool, error) {
+func parseNameVal(rest string, key string) (*Node, map[string]bool, error) {
 	// This is kind of tricky because we need to support the old
-	// variant:   ENV name value
-	// as well as the new one:    ENV name=value ...
+	// variant:   KEY name value
+	// as well as the new one:    KEY name=value ...
 	// The trigger to know which one is being used will be whether we hit
 	// a space or = first.  space ==> old, "=" ==> new
 
@@ -137,10 +137,10 @@ func parseEnv(rest string) (*Node, map[string]bool, error) {
 	}
 
 	if len(words) == 0 {
-		return nil, nil, fmt.Errorf("ENV requires at least one argument")
+		return nil, nil, fmt.Errorf(key + " requires at least one argument")
 	}
 
-	// Old format (ENV name value)
+	// Old format (KEY name value)
 	var rootnode *Node
 
 	if !strings.Contains(words[0], "=") {
@@ -149,7 +149,7 @@ func parseEnv(rest string) (*Node, map[string]bool, error) {
 		strs := TOKEN_WHITESPACE.Split(rest, 2)
 
 		if len(strs) < 2 {
-			return nil, nil, fmt.Errorf("ENV must have two arguments")
+			return nil, nil, fmt.Errorf(key + " must have two arguments")
 		}
 
 		node.Value = strs[0]
@@ -182,6 +182,14 @@ func parseEnv(rest string) (*Node, map[string]bool, error) {
 	return rootnode, nil, nil
 }
 
+func parseEnv(rest string) (*Node, map[string]bool, error) {
+	return parseNameVal(rest, "ENV")
+}
+
+func parseLabel(rest string) (*Node, map[string]bool, error) {
+	return parseNameVal(rest, "LABEL")
+}
+
 // parses a whitespace-delimited set of arguments. The result is effectively a
 // linked list of string arguments.
 func parseStringsWhitespaceDelimited(rest string) (*Node, map[string]bool, error) {

builder/parser/parser.go

@@ -50,6 +50,7 @@ func init() {
 		command.Onbuild:    parseSubCommand,
 		command.Workdir:    parseString,
 		command.Env:        parseEnv,
+		command.Label:      parseLabel,
 		command.Maintainer: parseString,
 		command.From:       parseString,
 		command.Add:        parseMaybeJSONToList,