builder/dispatchers.go - third_party/github.com/moby/moby - Git at Google

 package builder

 // This file contains the dispatchers for each command. Note that
 // `nullDispatch` is not actually a command, but support for commands we parse
 // but do nothing with.
 //
 // See evaluator.go for a higher level discussion of the whole evaluator
 // package.

 import (
 	"fmt"
 	"io/ioutil"
 	"path"
 	"path/filepath"
 	"regexp"
 	"runtime"
 	"sort"
 	"strings"

 	"github.com/Sirupsen/logrus"
 	flag "github.com/docker/docker/pkg/mflag"
 	"github.com/docker/docker/pkg/nat"
 	"github.com/docker/docker/runconfig"
 )

 const (
 	// NoBaseImageSpecifier is the symbol used by the FROM
 	// command to specify that no base image is to be used.
 	NoBaseImageSpecifier string = "scratch"
 )

 // dispatch with no layer / parsing. This is effectively not a command.
 func nullDispatch(b *builder, args []string, attributes map[string]bool, original string) error {
 	return nil
 }

 // ENV foo bar
 //
 // Sets the environment variable foo to bar, also makes interpolation
 // in the dockerfile available from the next statement on via ${foo}.
 //
 func env(b *builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) == 0 {
 		return fmt.Errorf("ENV requires at least one argument")
 	}

 	if len(args)%2 != 0 {
 		// should never get here, but just in case
 		return fmt.Errorf("Bad input to ENV, too many args")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	// TODO/FIXME/NOT USED
 	// Just here to show how to use the builder flags stuff within the
 	// context of a builder command. Will remove once we actually add
 	// a builder command to something!
 	/*
 		flBool1 := b.BuilderFlags.AddBool("bool1", false)
 		flStr1 := b.BuilderFlags.AddString("str1", "HI")

 		if err := b.BuilderFlags.Parse(); err != nil {
 			return err
 		}

 		fmt.Printf("Bool1:%v\n", flBool1)
 		fmt.Printf("Str1:%v\n", flStr1)
 	*/

 	commitStr := "ENV"

 	for j := 0; j < len(args); j++ {
 		// name  ==> args[j]
 		// value ==> args[j+1]
 		newVar := args[j] + "=" + args[j+1] + ""
 		commitStr += " " + newVar

 		gotOne := false
 		for i, envVar := range b.Config.Env {
 			envParts := strings.SplitN(envVar, "=", 2)
 			if envParts[0] == args[j] {
 				b.Config.Env[i] = newVar
 				gotOne = true
 				break
 			}
 		}
 		if !gotOne {
 			b.Config.Env = append(b.Config.Env, newVar)
 		}
 		j++
 	}

 	return b.commit("", b.Config.Cmd, commitStr)
 }

 // MAINTAINER some text <maybe@an.email.address>
 //
 // Sets the maintainer metadata.
 func maintainer(b *builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) != 1 {
 		return fmt.Errorf("MAINTAINER requires exactly one argument")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	b.maintainer = args[0]
 	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 requires at least one argument")
 	}
 	if len(args)%2 != 0 {
 		// should never get here, but just in case
 		return fmt.Errorf("Bad input to LABEL, too many args")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	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
 // exist here. If you do not wish to have this automatic handling, use COPY.
 //
 func add(b *builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) < 2 {
 		return fmt.Errorf("ADD requires at least two arguments")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	return b.runContextCommand(args, true, true, "ADD")
 }

 // COPY foo /path
 //
 // Same as 'ADD' but without the tar and remote url handling.
 //
 func dispatchCopy(b *builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) < 2 {
 		return fmt.Errorf("COPY requires at least two arguments")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	return b.runContextCommand(args, false, false, "COPY")
 }

 // FROM imagename
 //
 // This sets the image the dockerfile will build on top of.
 //
 func from(b *builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) != 1 {
 		return fmt.Errorf("FROM requires one argument")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	name := args[0]

 	if name == NoBaseImageSpecifier {
 		b.image = ""
 		b.noBaseImage = true
 		return nil
 	}

 	image, err := b.Daemon.Repositories().LookupImage(name)
 	if b.Pull {
 		image, err = b.pullImage(name)
 		if err != nil {
 			return err
 		}
 	}
 	if err != nil {
 		if b.Daemon.Graph().IsNotExist(err, name) {
 			image, err = b.pullImage(name)
 		}

 		// note that the top level err will still be !nil here if IsNotExist is
 		// not the error. This approach just simplifies the logic a bit.
 		if err != nil {
 			return err
 		}
 	}

 	return b.processImageFrom(image)
 }

 // ONBUILD RUN echo yo
 //
 // ONBUILD triggers run when the image is used in a FROM statement.
 //
 // ONBUILD handling has a lot of special-case functionality, the heading in
 // evaluator.go and comments around dispatch() in the same file explain the
 // special cases. search for 'OnBuild' in internals.go for additional special
 // cases.
 //
 func onbuild(b *builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) == 0 {
 		return fmt.Errorf("ONBUILD requires at least one argument")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	triggerInstruction := strings.ToUpper(strings.TrimSpace(args[0]))
 	switch triggerInstruction {
 	case "ONBUILD":
 		return fmt.Errorf("Chaining ONBUILD via `ONBUILD ONBUILD` isn't allowed")
 	case "MAINTAINER", "FROM":
 		return fmt.Errorf("%s isn't allowed as an ONBUILD trigger", triggerInstruction)
 	}

 	original = regexp.MustCompile(`(?i)^\s*ONBUILD\s*`).ReplaceAllString(original, "")

 	b.Config.OnBuild = append(b.Config.OnBuild, original)
 	return b.commit("", b.Config.Cmd, fmt.Sprintf("ONBUILD %s", original))
 }

 // WORKDIR /tmp
 //
 // Set the working directory for future RUN/CMD/etc statements.
 //
 func workdir(b *builder, args []string, attributes map[string]bool, original string) error {
 	if len(args) != 1 {
 		return fmt.Errorf("WORKDIR requires exactly one argument")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	// Note that workdir passed comes from the Dockerfile. Hence it is in
 	// Linux format using forward-slashes, even on Windows. However,
 	// b.Config.WorkingDir is in platform-specific notation (in other words
 	// on Windows will use `\`
 	workdir := args[0]

 	isAbs := false
 	if runtime.GOOS == "windows" {
 		// Alternate processing for Windows here is necessary as we can't call
 		// filepath.IsAbs(workDir) as that would verify Windows style paths,
 		// along with drive-letters (eg c:\pathto\file.txt). We (arguably
 		// correctly or not) check for both forward and back slashes as this
 		// is what the 1.4.2 GoLang implementation of IsAbs() does in the
 		// isSlash() function.
 		isAbs = workdir[0] == '\\' || workdir[0] == '/'
 	} else {
 		isAbs = filepath.IsAbs(workdir)
 	}

 	if !isAbs {
 		current := b.Config.WorkingDir
 		if runtime.GOOS == "windows" {
 			// Convert to Linux format before join
 			current = strings.Replace(current, "\\", "/", -1)
 		}
 		// Must use path.Join so works correctly on Windows, not filepath
 		workdir = path.Join("/", current, workdir)
 	}

 	// Convert to platform specific format
 	if runtime.GOOS == "windows" {
 		workdir = strings.Replace(workdir, "/", "\\", -1)
 	}
 	b.Config.WorkingDir = workdir

 	return b.commit("", b.Config.Cmd, fmt.Sprintf("WORKDIR %v", workdir))
 }

 // RUN some command yo
 //
 // run a command and commit the image. Args are automatically prepended with
 // 'sh -c' under linux or 'cmd /S /C' under Windows, in the event there is
 // only one argument. The difference in processing:
 //
 // RUN echo hi          # sh -c echo hi       (Linux)
 // RUN echo hi          # cmd /S /C echo hi   (Windows)
 // RUN [ "echo", "hi" ] # echo hi
 //
 func run(b *builder, args []string, attributes map[string]bool, original string) error {
 	if b.image == "" && !b.noBaseImage {
 		return fmt.Errorf("Please provide a source image with `from` prior to run")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	args = handleJSONArgs(args, attributes)

 	if !attributes["json"] {
 		if runtime.GOOS != "windows" {
 			args = append([]string{"/bin/sh", "-c"}, args...)
 		} else {
 			args = append([]string{"cmd", "/S /C"}, args...)
 		}
 	}

 	runCmd := flag.NewFlagSet("run", flag.ContinueOnError)
 	runCmd.SetOutput(ioutil.Discard)
 	runCmd.Usage = nil

 	config, _, _, err := runconfig.Parse(runCmd, append([]string{b.image}, args...))
 	if err != nil {
 		return err
 	}

 	cmd := b.Config.Cmd
 	// set Cmd manually, this is special case only for Dockerfiles
 	b.Config.Cmd = config.Cmd
 	runconfig.Merge(b.Config, config)

 	defer func(cmd *runconfig.Command) { b.Config.Cmd = cmd }(cmd)

 	logrus.Debugf("[BUILDER] Command to be executed: %v", b.Config.Cmd)

 	hit, err := b.probeCache()
 	if err != nil {
 		return err
 	}
 	if hit {
 		return nil
 	}

 	c, err := b.create()
 	if err != nil {
 		return err
 	}

 	// Ensure that we keep the container mounted until the commit
 	// to avoid unmounting and then mounting directly again
 	c.Mount()
 	defer c.Unmount()

 	err = b.run(c)
 	if err != nil {
 		return err
 	}
 	if err := b.commit(c.ID, cmd, "run"); err != nil {
 		return err
 	}

 	return nil
 }

 // CMD foo
 //
 // Set the default command to run in the container (which may be empty).
 // Argument handling is the same as RUN.
 //
 func cmd(b *builder, args []string, attributes map[string]bool, original string) error {
 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	cmdSlice := handleJSONArgs(args, attributes)

 	if !attributes["json"] {
 		if runtime.GOOS != "windows" {
 			cmdSlice = append([]string{"/bin/sh", "-c"}, cmdSlice...)
 		} else {
 			cmdSlice = append([]string{"cmd", "/S /C"}, cmdSlice...)
 		}
 	}

 	b.Config.Cmd = runconfig.NewCommand(cmdSlice...)

 	if err := b.commit("", b.Config.Cmd, fmt.Sprintf("CMD %q", cmdSlice)); err != nil {
 		return err
 	}

 	if len(args) != 0 {
 		b.cmdSet = true
 	}

 	return nil
 }

 // ENTRYPOINT /usr/sbin/nginx
 //
 // Set the entrypoint (which defaults to sh -c on linux, or cmd /S /C on Windows) to
 // /usr/sbin/nginx. Will accept the CMD as the arguments to /usr/sbin/nginx.
 //
 // Handles command processing similar to CMD and RUN, only b.Config.Entrypoint
 // is initialized at NewBuilder time instead of through argument parsing.
 //
 func entrypoint(b *builder, args []string, attributes map[string]bool, original string) error {
 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	parsed := handleJSONArgs(args, attributes)

 	switch {
 	case attributes["json"]:
 		// ENTRYPOINT ["echo", "hi"]
 		b.Config.Entrypoint = runconfig.NewEntrypoint(parsed...)
 	case len(parsed) == 0:
 		// ENTRYPOINT []
 		b.Config.Entrypoint = nil
 	default:
 		// ENTRYPOINT echo hi
 		if runtime.GOOS != "windows" {
 			b.Config.Entrypoint = runconfig.NewEntrypoint("/bin/sh", "-c", parsed[0])
 		} else {
 			b.Config.Entrypoint = runconfig.NewEntrypoint("cmd", "/S /C", parsed[0])
 		}
 	}

 	// when setting the entrypoint if a CMD was not explicitly set then
 	// set the command to nil
 	if !b.cmdSet {
 		b.Config.Cmd = nil
 	}

 	if err := b.commit("", b.Config.Cmd, fmt.Sprintf("ENTRYPOINT %q", b.Config.Entrypoint)); err != nil {
 		return err
 	}

 	return nil
 }

 // EXPOSE 6667/tcp 7000/tcp
 //
 // Expose ports for links and port mappings. This all ends up in
 // b.Config.ExposedPorts for runconfig.
 //
 func expose(b *builder, args []string, attributes map[string]bool, original string) error {
 	portsTab := args

 	if len(args) == 0 {
 		return fmt.Errorf("EXPOSE requires at least one argument")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	if b.Config.ExposedPorts == nil {
 		b.Config.ExposedPorts = make(nat.PortSet)
 	}

 	ports, _, err := nat.ParsePortSpecs(portsTab)
 	if err != nil {
 		return err
 	}

 	// instead of using ports directly, we build a list of ports and sort it so
 	// the order is consistent. This prevents cache burst where map ordering
 	// changes between builds
 	portList := make([]string, len(ports))
 	var i int
 	for port := range ports {
 		if _, exists := b.Config.ExposedPorts[port]; !exists {
 			b.Config.ExposedPorts[port] = struct{}{}
 		}
 		portList[i] = string(port)
 		i++
 	}
 	sort.Strings(portList)
 	return b.commit("", b.Config.Cmd, fmt.Sprintf("EXPOSE %s", strings.Join(portList, " ")))
 }

 // USER foo
 //
 // Set the user to 'foo' for future commands and when running the
 // ENTRYPOINT/CMD at container run time.
 //
 func user(b *builder, args []string, attributes map[string]bool, original string) error {
 	if runtime.GOOS == "windows" {
 		return fmt.Errorf("USER is not supported on Windows")
 	}

 	if len(args) != 1 {
 		return fmt.Errorf("USER requires exactly one argument")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	b.Config.User = args[0]
 	return b.commit("", b.Config.Cmd, fmt.Sprintf("USER %v", args))
 }

 // VOLUME /foo
 //
 // Expose the volume /foo for use. Will also accept the JSON array form.
 //
 func volume(b *builder, args []string, attributes map[string]bool, original string) error {
 	if runtime.GOOS == "windows" {
 		return fmt.Errorf("VOLUME is not supported on Windows")
 	}
 	if len(args) == 0 {
 		return fmt.Errorf("VOLUME requires at least one argument")
 	}

 	if err := b.BuilderFlags.Parse(); err != nil {
 		return err
 	}

 	if b.Config.Volumes == nil {
 		b.Config.Volumes = map[string]struct{}{}
 	}
 	for _, v := range args {
 		v = strings.TrimSpace(v)
 		if v == "" {
 			return fmt.Errorf("Volume specified can not be an empty string")
 		}
 		b.Config.Volumes[v] = struct{}{}
 	}
 	if err := b.commit("", b.Config.Cmd, fmt.Sprintf("VOLUME %v", args)); err != nil {
 		return err
 	}
 	return nil
 }
	package builder

	// This file contains the dispatchers for each command. Note that
	// `nullDispatch` is not actually a command, but support for commands we parse
	// but do nothing with.
	//
	// See evaluator.go for a higher level discussion of the whole evaluator
	// package.

	import (
	"fmt"
	"io/ioutil"
	"path"
	"path/filepath"
	"regexp"
	"runtime"
	"sort"
	"strings"

	"github.com/Sirupsen/logrus"
	flag "github.com/docker/docker/pkg/mflag"
	"github.com/docker/docker/pkg/nat"
	"github.com/docker/docker/runconfig"
	)

	const (
	// NoBaseImageSpecifier is the symbol used by the FROM
	// command to specify that no base image is to be used.
	NoBaseImageSpecifier string = "scratch"
	)

	// dispatch with no layer / parsing. This is effectively not a command.
	func nullDispatch(b *builder, args []string, attributes map[string]bool, original string) error {
	return nil
	}

	// ENV foo bar
	//
	// Sets the environment variable foo to bar, also makes interpolation
	// in the dockerfile available from the next statement on via ${foo}.
	//
	func env(b *builder, args []string, attributes map[string]bool, original string) error {
	if len(args) == 0 {
	return fmt.Errorf("ENV requires at least one argument")
	}

	if len(args)%2 != 0 {
	// should never get here, but just in case
	return fmt.Errorf("Bad input to ENV, too many args")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	// TODO/FIXME/NOT USED
	// Just here to show how to use the builder flags stuff within the
	// context of a builder command. Will remove once we actually add
	// a builder command to something!
	/*
	flBool1 := b.BuilderFlags.AddBool("bool1", false)
	flStr1 := b.BuilderFlags.AddString("str1", "HI")

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	fmt.Printf("Bool1:%v\n", flBool1)
	fmt.Printf("Str1:%v\n", flStr1)
	*/

	commitStr := "ENV"

	for j := 0; j < len(args); j++ {
	// name ==> args[j]
	// value ==> args[j+1]
	newVar := args[j] + "=" + args[j+1] + ""
	commitStr += " " + newVar

	gotOne := false
	for i, envVar := range b.Config.Env {
	envParts := strings.SplitN(envVar, "=", 2)
	if envParts[0] == args[j] {
	b.Config.Env[i] = newVar
	gotOne = true
	break
	}
	}
	if !gotOne {
	b.Config.Env = append(b.Config.Env, newVar)
	}
	j++
	}

	return b.commit("", b.Config.Cmd, commitStr)
	}

	// MAINTAINER some text <maybe@an.email.address>
	//
	// Sets the maintainer metadata.
	func maintainer(b *builder, args []string, attributes map[string]bool, original string) error {
	if len(args) != 1 {
	return fmt.Errorf("MAINTAINER requires exactly one argument")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	b.maintainer = args[0]
	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 requires at least one argument")
	}
	if len(args)%2 != 0 {
	// should never get here, but just in case
	return fmt.Errorf("Bad input to LABEL, too many args")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	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
	// exist here. If you do not wish to have this automatic handling, use COPY.
	//
	func add(b *builder, args []string, attributes map[string]bool, original string) error {
	if len(args) < 2 {
	return fmt.Errorf("ADD requires at least two arguments")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	return b.runContextCommand(args, true, true, "ADD")
	}

	// COPY foo /path
	//
	// Same as 'ADD' but without the tar and remote url handling.
	//
	func dispatchCopy(b *builder, args []string, attributes map[string]bool, original string) error {
	if len(args) < 2 {
	return fmt.Errorf("COPY requires at least two arguments")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	return b.runContextCommand(args, false, false, "COPY")
	}

	// FROM imagename
	//
	// This sets the image the dockerfile will build on top of.
	//
	func from(b *builder, args []string, attributes map[string]bool, original string) error {
	if len(args) != 1 {
	return fmt.Errorf("FROM requires one argument")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	name := args[0]

	if name == NoBaseImageSpecifier {
	b.image = ""
	b.noBaseImage = true
	return nil
	}

	image, err := b.Daemon.Repositories().LookupImage(name)
	if b.Pull {
	image, err = b.pullImage(name)
	if err != nil {
	return err
	}
	}
	if err != nil {
	if b.Daemon.Graph().IsNotExist(err, name) {
	image, err = b.pullImage(name)
	}

	// note that the top level err will still be !nil here if IsNotExist is
	// not the error. This approach just simplifies the logic a bit.
	if err != nil {
	return err
	}
	}

	return b.processImageFrom(image)
	}

	// ONBUILD RUN echo yo
	//
	// ONBUILD triggers run when the image is used in a FROM statement.
	//
	// ONBUILD handling has a lot of special-case functionality, the heading in
	// evaluator.go and comments around dispatch() in the same file explain the
	// special cases. search for 'OnBuild' in internals.go for additional special
	// cases.
	//
	func onbuild(b *builder, args []string, attributes map[string]bool, original string) error {
	if len(args) == 0 {
	return fmt.Errorf("ONBUILD requires at least one argument")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	triggerInstruction := strings.ToUpper(strings.TrimSpace(args[0]))
	switch triggerInstruction {
	case "ONBUILD":
	return fmt.Errorf("Chaining ONBUILD via `ONBUILD ONBUILD` isn't allowed")
	case "MAINTAINER", "FROM":
	return fmt.Errorf("%s isn't allowed as an ONBUILD trigger", triggerInstruction)
	}

	original = regexp.MustCompile(`(?i)^\sONBUILD\s`).ReplaceAllString(original, "")

	b.Config.OnBuild = append(b.Config.OnBuild, original)
	return b.commit("", b.Config.Cmd, fmt.Sprintf("ONBUILD %s", original))
	}

	// WORKDIR /tmp
	//
	// Set the working directory for future RUN/CMD/etc statements.
	//
	func workdir(b *builder, args []string, attributes map[string]bool, original string) error {
	if len(args) != 1 {
	return fmt.Errorf("WORKDIR requires exactly one argument")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	// Note that workdir passed comes from the Dockerfile. Hence it is in
	// Linux format using forward-slashes, even on Windows. However,
	// b.Config.WorkingDir is in platform-specific notation (in other words
	// on Windows will use `\`
	workdir := args[0]

	isAbs := false
	if runtime.GOOS == "windows" {
	// Alternate processing for Windows here is necessary as we can't call
	// filepath.IsAbs(workDir) as that would verify Windows style paths,
	// along with drive-letters (eg c:\pathto\file.txt). We (arguably
	// correctly or not) check for both forward and back slashes as this
	// is what the 1.4.2 GoLang implementation of IsAbs() does in the
	// isSlash() function.
	isAbs = workdir[0] == '\\' \|\| workdir[0] == '/'
	} else {
	isAbs = filepath.IsAbs(workdir)
	}

	if !isAbs {
	current := b.Config.WorkingDir
	if runtime.GOOS == "windows" {
	// Convert to Linux format before join
	current = strings.Replace(current, "\\", "/", -1)
	}
	// Must use path.Join so works correctly on Windows, not filepath
	workdir = path.Join("/", current, workdir)
	}

	// Convert to platform specific format
	if runtime.GOOS == "windows" {
	workdir = strings.Replace(workdir, "/", "\\", -1)
	}
	b.Config.WorkingDir = workdir

	return b.commit("", b.Config.Cmd, fmt.Sprintf("WORKDIR %v", workdir))
	}

	// RUN some command yo
	//
	// run a command and commit the image. Args are automatically prepended with
	// 'sh -c' under linux or 'cmd /S /C' under Windows, in the event there is
	// only one argument. The difference in processing:
	//
	// RUN echo hi # sh -c echo hi (Linux)
	// RUN echo hi # cmd /S /C echo hi (Windows)
	// RUN [ "echo", "hi" ] # echo hi
	//
	func run(b *builder, args []string, attributes map[string]bool, original string) error {
	if b.image == "" && !b.noBaseImage {
	return fmt.Errorf("Please provide a source image with `from` prior to run")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	args = handleJSONArgs(args, attributes)

	if !attributes["json"] {
	if runtime.GOOS != "windows" {
	args = append([]string{"/bin/sh", "-c"}, args...)
	} else {
	args = append([]string{"cmd", "/S /C"}, args...)
	}
	}

	runCmd := flag.NewFlagSet("run", flag.ContinueOnError)
	runCmd.SetOutput(ioutil.Discard)
	runCmd.Usage = nil

	config, _, _, err := runconfig.Parse(runCmd, append([]string{b.image}, args...))
	if err != nil {
	return err
	}

	cmd := b.Config.Cmd
	// set Cmd manually, this is special case only for Dockerfiles
	b.Config.Cmd = config.Cmd
	runconfig.Merge(b.Config, config)

	defer func(cmd *runconfig.Command) { b.Config.Cmd = cmd }(cmd)

	logrus.Debugf("[BUILDER] Command to be executed: %v", b.Config.Cmd)

	hit, err := b.probeCache()
	if err != nil {
	return err
	}
	if hit {
	return nil
	}

	c, err := b.create()
	if err != nil {
	return err
	}

	// Ensure that we keep the container mounted until the commit
	// to avoid unmounting and then mounting directly again
	c.Mount()
	defer c.Unmount()

	err = b.run(c)
	if err != nil {
	return err
	}
	if err := b.commit(c.ID, cmd, "run"); err != nil {
	return err
	}

	return nil
	}

	// CMD foo
	//
	// Set the default command to run in the container (which may be empty).
	// Argument handling is the same as RUN.
	//
	func cmd(b *builder, args []string, attributes map[string]bool, original string) error {
	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	cmdSlice := handleJSONArgs(args, attributes)

	if !attributes["json"] {
	if runtime.GOOS != "windows" {
	cmdSlice = append([]string{"/bin/sh", "-c"}, cmdSlice...)
	} else {
	cmdSlice = append([]string{"cmd", "/S /C"}, cmdSlice...)
	}
	}

	b.Config.Cmd = runconfig.NewCommand(cmdSlice...)

	if err := b.commit("", b.Config.Cmd, fmt.Sprintf("CMD %q", cmdSlice)); err != nil {
	return err
	}

	if len(args) != 0 {
	b.cmdSet = true
	}

	return nil
	}

	// ENTRYPOINT /usr/sbin/nginx
	//
	// Set the entrypoint (which defaults to sh -c on linux, or cmd /S /C on Windows) to
	// /usr/sbin/nginx. Will accept the CMD as the arguments to /usr/sbin/nginx.
	//
	// Handles command processing similar to CMD and RUN, only b.Config.Entrypoint
	// is initialized at NewBuilder time instead of through argument parsing.
	//
	func entrypoint(b *builder, args []string, attributes map[string]bool, original string) error {
	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	parsed := handleJSONArgs(args, attributes)

	switch {
	case attributes["json"]:
	// ENTRYPOINT ["echo", "hi"]
	b.Config.Entrypoint = runconfig.NewEntrypoint(parsed...)
	case len(parsed) == 0:
	// ENTRYPOINT []
	b.Config.Entrypoint = nil
	default:
	// ENTRYPOINT echo hi
	if runtime.GOOS != "windows" {
	b.Config.Entrypoint = runconfig.NewEntrypoint("/bin/sh", "-c", parsed[0])
	} else {
	b.Config.Entrypoint = runconfig.NewEntrypoint("cmd", "/S /C", parsed[0])
	}
	}

	// when setting the entrypoint if a CMD was not explicitly set then
	// set the command to nil
	if !b.cmdSet {
	b.Config.Cmd = nil
	}

	if err := b.commit("", b.Config.Cmd, fmt.Sprintf("ENTRYPOINT %q", b.Config.Entrypoint)); err != nil {
	return err
	}

	return nil
	}

	// EXPOSE 6667/tcp 7000/tcp
	//
	// Expose ports for links and port mappings. This all ends up in
	// b.Config.ExposedPorts for runconfig.
	//
	func expose(b *builder, args []string, attributes map[string]bool, original string) error {
	portsTab := args

	if len(args) == 0 {
	return fmt.Errorf("EXPOSE requires at least one argument")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	if b.Config.ExposedPorts == nil {
	b.Config.ExposedPorts = make(nat.PortSet)
	}

	ports, _, err := nat.ParsePortSpecs(portsTab)
	if err != nil {
	return err
	}

	// instead of using ports directly, we build a list of ports and sort it so
	// the order is consistent. This prevents cache burst where map ordering
	// changes between builds
	portList := make([]string, len(ports))
	var i int
	for port := range ports {
	if _, exists := b.Config.ExposedPorts[port]; !exists {
	b.Config.ExposedPorts[port] = struct{}{}
	}
	portList[i] = string(port)
	i++
	}
	sort.Strings(portList)
	return b.commit("", b.Config.Cmd, fmt.Sprintf("EXPOSE %s", strings.Join(portList, " ")))
	}

	// USER foo
	//
	// Set the user to 'foo' for future commands and when running the
	// ENTRYPOINT/CMD at container run time.
	//
	func user(b *builder, args []string, attributes map[string]bool, original string) error {
	if runtime.GOOS == "windows" {
	return fmt.Errorf("USER is not supported on Windows")
	}

	if len(args) != 1 {
	return fmt.Errorf("USER requires exactly one argument")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	b.Config.User = args[0]
	return b.commit("", b.Config.Cmd, fmt.Sprintf("USER %v", args))
	}

	// VOLUME /foo
	//
	// Expose the volume /foo for use. Will also accept the JSON array form.
	//
	func volume(b *builder, args []string, attributes map[string]bool, original string) error {
	if runtime.GOOS == "windows" {
	return fmt.Errorf("VOLUME is not supported on Windows")
	}
	if len(args) == 0 {
	return fmt.Errorf("VOLUME requires at least one argument")
	}

	if err := b.BuilderFlags.Parse(); err != nil {
	return err
	}

	if b.Config.Volumes == nil {
	b.Config.Volumes = map[string]struct{}{}
	}
	for _, v := range args {
	v = strings.TrimSpace(v)
	if v == "" {
	return fmt.Errorf("Volume specified can not be an empty string")
	}
	b.Config.Volumes[v] = struct{}{}
	}
	if err := b.commit("", b.Config.Cmd, fmt.Sprintf("VOLUME %v", args)); err != nil {
	return err
	}
	return nil
	}