Add `docker build --iidfile=FILE`

This is synonymous with `docker run --cidfile=FILE` and writes the digest of
the newly built image to the named file. This is intended to be used by build
systems which want to avoid tagging (perhaps because they are in CI or
otherwise want to avoid fixed names which can clash) by enabling e.g. Makefile
constructs like:

    image.id: Dockerfile
    	docker build --iidfile=image.id .

    do-some-more-stuff: image.id
    	do-stuff-with <image.id

Currently the only way to achieve this is to use `docker build -q` and capture
the stdout, but at the expense of losing the build output.

In non-silent mode (without `-q`) with API >= v1.29 the caller will now see a
`JSONMessage` with the `Aux` field containing a `types.BuildResult` in the
output stream for each image/layer produced during the build, with the final
one being the end product.  Having all of the intermediate images might be
interesting in some cases.

In silent mode (with `-q`) there is no change, on success the only output will
be the resulting image digest as it was previosuly.

There was no wrapper to just output an Aux section without enclosing it in a
Progress, so add one here.

Added some tests to integration cli tests.

Signed-off-by: Ian Campbell <ian.campbell@docker.com>

cli/command/image/build.go

@@ -4,8 +4,10 @@ import (
 	"archive/tar"
 	"bufio"
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"regexp"
 	"runtime"
@@ -59,6 +61,7 @@ type buildOptions struct {
 	networkMode    string
 	squash         bool
 	target         string
+	imageIDFile    string
 }
 
 // dockerfileFromStdin returns true when the user specified that the Dockerfile
@@ -123,6 +126,7 @@ func NewBuildCommand(dockerCli *command.DockerCli) *cobra.Command {
 	flags.SetAnnotation("network", "version", []string{"1.25"})
 	flags.Var(&options.extraHosts, "add-host", "Add a custom host-to-IP mapping (host:ip)")
 	flags.StringVar(&options.target, "target", "", "Set the target build stage to build.")
+	flags.StringVar(&options.imageIDFile, "iidfile", "", "Write the image ID to the file")
 
 	command.AddTrustVerificationFlags(flags)
 
@@ -176,6 +180,12 @@ func runBuild(dockerCli *command.DockerCli, options buildOptions) error {
 		progBuff = bytes.NewBuffer(nil)
 		buildBuff = bytes.NewBuffer(nil)
 	}
+	if options.imageIDFile != "" {
+		// Avoid leaving a stale file if we eventually fail
+		if err := os.Remove(options.imageIDFile); err != nil && !os.IsNotExist(err) {
+			return errors.Wrap(err, "Removing image ID file")
+		}
+	}
 
 	switch {
 	case options.contextFromStdin():
@@ -301,7 +311,17 @@ func runBuild(dockerCli *command.DockerCli, options buildOptions) error {
 	}
 	defer response.Body.Close()
 
-	err = jsonmessage.DisplayJSONMessagesStream(response.Body, buildBuff, dockerCli.Out().FD(), dockerCli.Out().IsTerminal(), nil)
+	imageID := ""
+	aux := func(auxJSON *json.RawMessage) {
+		var result types.BuildResult
+		if err := json.Unmarshal(*auxJSON, &result); err != nil {
+			fmt.Fprintf(dockerCli.Err(), "Failed to parse aux message: %s", err)
+		} else {
+			imageID = result.ID
+		}
+	}
+
+	err = jsonmessage.DisplayJSONMessagesStream(response.Body, buildBuff, dockerCli.Out().FD(), dockerCli.Out().IsTerminal(), aux)
 	if err != nil {
 		if jerr, ok := err.(*jsonmessage.JSONError); ok {
 			// If no error code is set, default to 1
@@ -329,9 +349,18 @@ func runBuild(dockerCli *command.DockerCli, options buildOptions) error {
 	// Everything worked so if -q was provided the output from the daemon
 	// should be just the image ID and we'll print that to stdout.
 	if options.quiet {
-		fmt.Fprintf(dockerCli.Out(), "%s", buildBuff)
+		imageID = fmt.Sprintf("%s", buildBuff)
+		fmt.Fprintf(dockerCli.Out(), imageID)
 	}
 
+	if options.imageIDFile != "" {
+		if imageID == "" {
+			return errors.Errorf("Server did not provide an image ID. Cannot write %s", options.imageIDFile)
+		}
+		if err := ioutil.WriteFile(options.imageIDFile, []byte(imageID), 0666); err != nil {
+			return err
+		}
+	}
 	if command.IsTrusted() {
 		// Since the build was successful, now we must tag any of the resolved
 		// images from the above Dockerfile rewrite.

vendor.conf

@@ -6,7 +6,7 @@ github.com/agl/ed25519 d2b94fd789ea21d12fac1a4443dd3a3f79cda72c
 github.com/coreos/etcd 824277cb3a577a0e8c829ca9ec557b973fe06d20
 github.com/davecgh/go-spew 346938d642f2ec3594ed81d874461961cd0faa76
 github.com/docker/distribution b38e5838b7b2f2ad48e06ec4b500011976080621
-github.com/docker/docker bf5cf84534f1eac9805c6f1bffff341358806b57
+github.com/docker/docker d624f9a7b00419179eb0e7e81f2894dde0752873
 github.com/docker/docker-credential-helpers v0.5.0
 github.com/docker/go d30aec9fd63c35133f8f79c3412ad91a3b08be06
 github.com/docker/go-connections e15c02316c12de00874640cd76311849de2aeed5

vendor/github.com/docker/docker/api/types/types.go

@@ -530,3 +530,8 @@ type PushResult struct {
 	Digest string
 	Size   int
 }
+
+// BuildResult contains the image id of a successful build
+type BuildResult struct {
+	ID string
+}

vendor/github.com/docker/docker/pkg/jsonmessage/jsonmessage.go

@@ -109,7 +109,7 @@ type JSONMessage struct {
 	TimeNano        int64         `json:"timeNano,omitempty"`
 	Error           *JSONError    `json:"errorDetail,omitempty"`
 	ErrorMessage    string        `json:"error,omitempty"` //deprecated
-	// Aux contains out-of-band data, such as digests for push signing.
+	// Aux contains out-of-band data, such as digests for push signing and image id after building.
 	Aux *json.RawMessage `json:"aux,omitempty"`
 }
 

vendor/github.com/docker/docker/pkg/streamformatter/streamformatter.go

@@ -132,3 +132,28 @@ func (out *progressOutput) WriteProgress(prog progress.Progress) error {
 
 	return nil
 }
+
+// AuxFormatter is a streamFormatter that writes aux progress messages
+type AuxFormatter struct {
+	io.Writer
+}
+
+// Emit emits the given interface as an aux progress message
+func (sf *AuxFormatter) Emit(aux interface{}) error {
+	auxJSONBytes, err := json.Marshal(aux)
+	if err != nil {
+		return err
+	}
+	auxJSON := new(json.RawMessage)
+	*auxJSON = auxJSONBytes
+	msgJSON, err := json.Marshal(&jsonmessage.JSONMessage{Aux: auxJSON})
+	if err != nil {
+		return err
+	}
+	msgJSON = appendNewline(msgJSON)
+	n, err := sf.Writer.Write(msgJSON)
+	if n != len(msgJSON) {
+		return io.ErrShortWrite
+	}
+	return err
+}

vendor/github.com/docker/docker/vendor.conf

@@ -41,7 +41,7 @@ github.com/vishvananda/netlink 1e86b2bee5b6a7d377e4c02bb7f98209d6a7297c
 github.com/BurntSushi/toml f706d00e3de6abe700c994cdd545a1a4915af060
 github.com/samuel/go-zookeeper d0e0d8e11f318e000a8cc434616d69e329edc374
 github.com/deckarep/golang-set ef32fa3046d9f249d399f98ebaf9be944430fd1d
-github.com/coreos/etcd 824277cb3a577a0e8c829ca9ec557b973fe06d20
+github.com/coreos/etcd ea5389a79f40206170582c1ea076191b8622cb8e https://github.com/aaronlehmann/etcd # for https://github.com/coreos/etcd/pull/7830
 github.com/ugorji/go f1f1a805ed361a0e078bb537e4ea78cd37dcf065
 github.com/hashicorp/consul v0.5.2
 github.com/boltdb/bolt fff57c100f4dea1905678da7e90d92429dff2904
@@ -108,7 +108,7 @@ github.com/docker/containerd 9048e5e50717ea4497b757314bad98ea3763c145
 github.com/tonistiigi/fifo 1405643975692217d6720f8b54aeee1bf2cd5cf4
 
 # cluster
-github.com/docker/swarmkit 61a92e8ec074df5769decda985df4a3ab43c77eb
+github.com/docker/swarmkit 8f053c2030ebfc90f19f241fb7880e95b9761b7a
 github.com/gogo/protobuf 8d70fb3182befc465c4a1eac8ad4d38ff49778e2
 github.com/cloudflare/cfssl 7fb22c8cba7ecaf98e4082d22d65800cf45e042a
 github.com/google/certificate-transparency d90e65c3a07988180c5b1ece71791c0b6506826e