Fix image's `CMD` after `WORKDIR` in Dockerfile

This fix tries to fix 29667 where image's `CMD` is modified
after `WORKDIR` in Dockerfile.

The value of `b.runConfig.Cmd` was modified in the processing
of `WORKDIR`, in order to fix 28902. However, the same
`b.runConfig.Cmd` is passed to `commit()`.

This fix restored the `b.runConfig.Cmd` before `commit()`
the image for `WORKDIR`.

A test has been added.

This fix fixes 29667.

This fix is related to 28902, 28909, 28514.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

builder/dockerfile/dispatchers.go

@@ -297,17 +297,17 @@ func workdir(b *Builder, args []string, attributes map[string]bool, original str
 	}
 	b.runConfig.Image = b.image
 
-	cmd := b.runConfig.Cmd
-	b.runConfig.Cmd = strslice.StrSlice(append(getShell(b.runConfig), fmt.Sprintf("#(nop) WORKDIR %s", b.runConfig.WorkingDir)))
-	defer func(cmd strslice.StrSlice) { b.runConfig.Cmd = cmd }(cmd)
-
 	if hit, err := b.probeCache(); err != nil {
 		return err
 	} else if hit {
 		return nil
 	}
 
-	container, err := b.docker.ContainerCreate(types.ContainerCreateConfig{Config: b.runConfig})
+	// Actually copy the struct
+	workdirConfig := *b.runConfig
+	workdirConfig.Cmd = strslice.StrSlice(append(getShell(b.runConfig), fmt.Sprintf("#(nop) WORKDIR %s", b.runConfig.WorkingDir)))
+
+	container, err := b.docker.ContainerCreate(types.ContainerCreateConfig{Config: &workdirConfig})
 	if err != nil {
 		return err
 	}

integration-cli/docker_cli_build_test.go

@@ -7357,3 +7357,43 @@ func (s *DockerSuite) TestBuildWindowsEnvCaseInsensitive(c *check.C) {
 		c.Fatalf("Case insensitive environment variables on Windows failed. Got %s", res)
 	}
 }
+
+// Test case for 29667
+func (s *DockerSuite) TestBuildWorkdirImageCmd(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+
+	image := "testworkdirimagecmd"
+	dockerfile := `
+FROM busybox
+WORKDIR /foo/bar
+`
+	out, err := buildImage(image, dockerfile, true)
+	c.Assert(err, checker.IsNil, check.Commentf("Output: %s", out))
+
+	out, _ = dockerCmd(c, "inspect", "--format", "{{ json .Config.Cmd }}", image)
+	c.Assert(strings.TrimSpace(out), checker.Equals, `["sh"]`)
+
+	image = "testworkdirlabelimagecmd"
+	dockerfile = `
+FROM busybox
+WORKDIR /foo/bar
+LABEL a=b
+`
+	out, err = buildImage(image, dockerfile, true)
+	c.Assert(err, checker.IsNil, check.Commentf("Output: %s", out))
+
+	out, _ = dockerCmd(c, "inspect", "--format", "{{ json .Config.Cmd }}", image)
+	c.Assert(strings.TrimSpace(out), checker.Equals, `["sh"]`)
+}
+
+// Test case for 28902/28090
+func (s *DockerSuite) TestBuildWorkdirCmd(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+
+	dockerFile := `
+                FROM golang:1.7-alpine
+                WORKDIR /
+                `
+	_, err := buildImage("testbuildworkdircmd", dockerFile, false)
+	c.Assert(err, checker.IsNil)
+}