@@ -129,6 +129,8 @@ type Backend interface {

 	ContainerWait(containerID string, timeout time.Duration) (int, error)

 	// ContainerUpdateCmdOnBuild updates container.Path and container.Args

 	ContainerUpdateCmdOnBuild(containerID string, cmd []string) error

+	// ContainerCreateWorkdir creates the workdir (currently only used on Windows)

+	ContainerCreateWorkdir(containerID string) error

 	// ContainerCopy copies/extracts a source FileInfo to a destination path inside a container

 	// specified by a container object.

@@ -18,6 +18,7 @@ import (

 	"github.com/Sirupsen/logrus"

 	"github.com/docker/docker/api"

+	"github.com/docker/docker/api/types"

 	"github.com/docker/docker/api/types/container"

 	"github.com/docker/docker/api/types/strslice"

 	"github.com/docker/docker/builder"

@@ -279,12 +280,26 @@ func workdir(b *Builder, args []string, attributes map[string]bool, original str

 		return err

 	}

-	// NOTE: You won't find the "mkdir" for the directory in here. Rather we

-	// just set the value in the image's runConfig.WorkingDir property

-	// and container.SetupWorkingDirectory() will create it automatically

-	// for us the next time the image is used to create a container.

+	// For performance reasons, we explicitly do a create/mkdir now

+	// This avoids having an unnecessary expensive mount/unmount calls

+	// (on Windows in particular) during each container create.

+	// Prior to 1.13, the mkdir was deferred and not executed at this step.

+	if b.disableCommit {

+		// Don't call back into the daemon if we're going through docker commit --change "WORKDIR /foo".

+		// We've already updated the runConfig and that's enough.

+		return nil

+	}

+	b.runConfig.Image = b.image

+	container, err := b.docker.ContainerCreate(types.ContainerCreateConfig{Config: b.runConfig}, true)

+	if err != nil {

+		return err

+	}

+	b.tmpContainers[container.ID] = struct{}{}

+	if err := b.docker.ContainerCreateWorkdir(container.ID); err != nil {

+		return err

+	}

-	return b.commit("", b.runConfig.Cmd, fmt.Sprintf("WORKDIR %v", b.runConfig.WorkingDir))

+	return b.commit(container.ID, b.runConfig.Cmd, "WORKDIR "+b.runConfig.WorkingDir)

 }

 // RUN some command yo

new file mode 100644

@@ -0,0 +1,21 @@

+package daemon

+

+// ContainerCreateWorkdir creates the working directory. This is solves the

+// issue arising from https://github.com/docker/docker/issues/27545,

+// which was initially fixed by https://github.com/docker/docker/pull/27884. But that fix

+// was too expensive in terms of performance on Windows. Instead,

+// https://github.com/docker/docker/pull/28514 introduces this new functionality

+// where the builder calls into the backend here to create the working directory.

+func (daemon *Daemon) ContainerCreateWorkdir(cID string) error {

+	container, err := daemon.GetContainer(cID)

+	if err != nil {

+		return err

+	}

+	err = daemon.Mount(container)

+	if err != nil {

+		return err

+	}

+	defer daemon.Unmount(container)

+	rootUID, rootGID := daemon.GetRemappedUIDGID()

+	return container.SetupWorkingDirectory(rootUID, rootGID)

+}

@@ -1878,8 +1878,8 @@ func (s *DockerSuite) TestBuildWindowsAddCopyPathProcessing(c *check.C) {

 			WORKDIR /wc2

 			ADD wc2 c:/wc2

 			WORKDIR c:/

-			RUN sh -c "[ $(cat c:/wc1) = 'hellowc1' ]"

-			RUN sh -c "[ $(cat c:/wc2) = 'worldwc2' ]"

+			RUN sh -c "[ $(cat c:/wc1/wc1) = 'hellowc1' ]"

+			RUN sh -c "[ $(cat c:/wc2/wc2) = 'worldwc2' ]"

 			# Trailing slash on COPY/ADD, Windows-style path.

 			WORKDIR /wd1

@@ -7283,3 +7283,31 @@ func (s *DockerSuite) TestBuildWindowsUser(c *check.C) {

 	}

 	c.Assert(strings.ToLower(out), checker.Contains, "username=user")

 }

+

+// Verifies if COPY file . when WORKDIR is set to a non-existing directory,

+// the directory is created and the file is copied into the directory,

+// as opposed to the file being copied as a file with the name of the

+// directory. Fix for 27545 (found on Windows, but regression good for Linux too).

+// Note 27545 was reverted in 28505, but a new fix was added subsequently in 28514.

+func (s *DockerSuite) TestBuildCopyFileDotWithWorkdir(c *check.C) {

+	name := "testbuildcopyfiledotwithworkdir"

+	ctx, err := fakeContext(`FROM busybox 

+WORKDIR /foo 

+COPY file . 

+RUN ["cat", "/foo/file"] 

+`,

+		map[string]string{})

+

+	if err != nil {

+		c.Fatal(err)

+	}

+	defer ctx.Close()

+

+	if err := ctx.Add("file", "content"); err != nil {

+		c.Fatal(err)

+	}

+

+	if _, err = buildImageFromContext(name, ctx, true); err != nil {

+		c.Fatal(err)

+	}

+}

@@ -104,7 +104,6 @@ func (s *DockerSuite) TestCommitWithHostBindMount(c *check.C) {

 }

 func (s *DockerSuite) TestCommitChange(c *check.C) {

-	testRequires(c, DaemonIsLinux)

 	dockerCmd(c, "run", "--name", "test", "busybox", "true")

 	imageID, _ := dockerCmd(c, "commit",

@@ -122,12 +121,14 @@ func (s *DockerSuite) TestCommitChange(c *check.C) {

 		"test", "test-commit")

 	imageID = strings.TrimSpace(imageID)

+	prefix, slash := getPrefixAndSlashFromDaemonPlatform()

+	prefix = strings.ToUpper(prefix) // Force C: as that's how WORKDIR is normalised on Windows

 	expected := map[string]string{

 		"Config.ExposedPorts": "map[8080/tcp:{}]",

 		"Config.Env":          "[DEBUG=true test=1 PATH=/foo]",

 		"Config.Labels":       "map[foo:bar]",

 		"Config.Cmd":          "[/bin/sh]",

-		"Config.WorkingDir":   "/opt",

+		"Config.WorkingDir":   prefix + slash + "opt",

 		"Config.Entrypoint":   "[/bin/sh]",

 		"Config.User":         "testuser",

 		"Config.Volumes":      "map[/var/lib/docker:{}]",