Fix ONBUILD COPY

the source was missing from the second dispatch

Signed-off-by: Daniel Nephin <dnephin@docker.com>
(cherry picked from commit 3f2604157790408acf5ad05c74cebe105f2b6979)

components/engine/integration-cli/cli/build/fakecontext/context.go

@@ -2,9 +2,12 @@ package fakecontext
 
 import (
 	"bytes"
+	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
+
+	"github.com/docker/docker/pkg/archive"
 )
 
 type testingT interface {
@@ -110,3 +113,12 @@ func (f *Fake) Delete(file string) error {
 func (f *Fake) Close() error {
 	return os.RemoveAll(f.Dir)
 }
+
+// AsTarReader returns a ReadCloser with the contents of Dir as a tar archive.
+func (f *Fake) AsTarReader(t testingT) io.ReadCloser {
+	reader, err := archive.TarWithOptions(f.Dir, &archive.TarOptions{})
+	if err != nil {
+		t.Fatalf("Failed to create tar from %s: %s", f.Dir, err)
+	}
+	return reader
+}

components/engine/integration-cli/docker_api_build_test.go

@@ -249,3 +249,28 @@ func (s *DockerSuite) TestBuildAPIUnnormalizedTarPaths(c *check.C) {
 
 	c.Assert(imageA, checker.Not(checker.Equals), imageB)
 }
+
+func (s *DockerSuite) TestBuildOnBuildWithCopy(c *check.C) {
+	dockerfile := `
+		FROM ` + minimalBaseImage() + ` as onbuildbase
+		ONBUILD COPY file /file
+
+		FROM onbuildbase
+	`
+	ctx := fakecontext.New(c, "",
+		fakecontext.WithDockerfile(dockerfile),
+		fakecontext.WithFile("file", "some content"),
+	)
+	defer ctx.Close()
+
+	res, body, err := request.Post(
+		"/build",
+		request.RawContent(ctx.AsTarReader(c)),
+		request.ContentType("application/x-tar"))
+	c.Assert(err, checker.IsNil)
+	c.Assert(res.StatusCode, checker.Equals, http.StatusOK)
+
+	out, err := testutil.ReadBody(body)
+	c.Assert(err, checker.IsNil)
+	c.Assert(string(out), checker.Contains, "Successfully built")
+}