Add `--file` flag for `docker secret create` command

This fix tries to address the issue raised in 28581 and 28927
where it is not possible to create a secret from a file (only
through STDIN).

This fix add a flag `--file` to `docker secret create` so that
it is possible to create a secret from a file with:
```
docker secret create --file secret.in secret.name
```

or
```
echo TEST | docker secret create --file - secret.name
```

Related docs has been updated.

An integration test has been added to cover the changes.

This fix fixes 28581.
This fix is related to 28927.

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

cli/command/secret/create.go

@@ -2,13 +2,14 @@ package secret
 
 import (
 	"fmt"
+	"io"
 	"io/ioutil"
-	"os"
 
 	"github.com/docker/docker/api/types/swarm"
 	"github.com/docker/docker/cli"
 	"github.com/docker/docker/cli/command"
 	"github.com/docker/docker/opts"
+	"github.com/docker/docker/pkg/system"
 	runconfigopts "github.com/docker/docker/runconfig/opts"
 	"github.com/spf13/cobra"
 	"golang.org/x/net/context"
@@ -16,6 +17,7 @@ import (
 
 type createOptions struct {
 	name   string
+	file   string
 	labels opts.ListOpts
 }
 
@@ -26,7 +28,7 @@ func newSecretCreateCommand(dockerCli *command.DockerCli) *cobra.Command {
 
 	cmd := &cobra.Command{
 		Use:   "create [OPTIONS] SECRET",
-		Short: "Create a secret using stdin as content",
+		Short: "Create a secret from a file or STDIN as content",
 		Args:  cli.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			createOpts.name = args[0]
@@ -35,6 +37,7 @@ func newSecretCreateCommand(dockerCli *command.DockerCli) *cobra.Command {
 	}
 	flags := cmd.Flags()
 	flags.VarP(&createOpts.labels, "label", "l", "Secret labels")
+	flags.StringVarP(&createOpts.file, "file", "f", "", "Read from a file or STDIN ('-')")
 
 	return cmd
 }
@@ -43,9 +46,23 @@ func runSecretCreate(dockerCli *command.DockerCli, options createOptions) error
 	client := dockerCli.Client()
 	ctx := context.Background()
 
-	secretData, err := ioutil.ReadAll(os.Stdin)
+	if options.file == "" {
+		return fmt.Errorf("Please specify either a file name or STDIN ('-') with --file")
+	}
+
+	var in io.Reader = dockerCli.In()
+	if options.file != "-" {
+		file, err := system.OpenSequential(options.file)
+		if err != nil {
+			return err
+		}
+		in = file
+		defer file.Close()
+	}
+
+	secretData, err := ioutil.ReadAll(in)
 	if err != nil {
-		return fmt.Errorf("Error reading content from STDIN: %v", err)
+		return fmt.Errorf("Error reading content from %q: %v", options.file, err)
 	}
 
 	spec := swarm.SecretSpec{

docs/reference/commandline/secret_create.md

@@ -16,15 +16,17 @@ keywords: ["secret, create"]
 # secret create
 
 ```Markdown
-Usage:  docker secret create [OPTIONS] SECRET
+Usage:	docker secret create [OPTIONS] SECRET
+
+Create a secret from a file or STDIN as content
 
-Create a secret using stdin as content
 Options:
-      --help         Print usage
-  -l, --label list   Secret labels (default [])
+  -f, --file string   Read from a file or STDIN ('-')
+      --help          Print usage
+  -l, --label list    Secret labels (default [])
 ```
 
-Creates a secret using standard input for the secret content. You must run this
+Creates a secret using standard input or from a file for the secret content. You must run this
 command on a manager node.
 
 ## Examples
@@ -32,7 +34,18 @@ command on a manager node.
 ### Create a secret
 
 ```bash
-$ cat secret.json | docker secret create secret.json
+$ cat secret.json | docker secret create -f - secret.json
+mhv17xfe3gh6xc4rij5orpfds
+
+$ docker secret ls
+ID                          NAME                    CREATED                                   UPDATED                                   SIZE
+mhv17xfe3gh6xc4rij5orpfds   secret.json             2016-10-27 23:25:43.909181089 +0000 UTC   2016-10-27 23:25:43.909181089 +0000 UTC   1679
+```
+
+### Create a secret with a file
+
+```bash
+$ docker secret create --file secret.in secret.json
 mhv17xfe3gh6xc4rij5orpfds
 
 $ docker secret ls
@@ -43,7 +56,7 @@ mhv17xfe3gh6xc4rij5orpfds   secret.json             2016-10-27 23:25:43.90918108
 ### Create a secret with labels
 
 ```bash
-$ cat secret.json | docker secret create secret.json --label env=dev --label rev=20161102
+$ cat secret.json | docker secret create secret.json -f - --label env=dev --label rev=20161102
 jtn7g6aukl5ky7nr9gvwafoxh
 
 $ docker secret inspect secret.json

integration-cli/docker_cli_secret_create_test.go

@@ -3,6 +3,10 @@
 package main
 
 import (
+	"io/ioutil"
+	"os"
+	"strings"
+
 	"github.com/docker/docker/api/types/swarm"
 	"github.com/docker/docker/pkg/integration/checker"
 	"github.com/go-check/check"
@@ -104,3 +108,33 @@ func (s *DockerSwarmSuite) TestSecretCreateResolve(c *check.C) {
 	c.Assert(out, checker.Not(checker.Contains), id)
 	c.Assert(out, checker.Not(checker.Contains), fake)
 }
+
+func (s *DockerSwarmSuite) TestSecretCreateWithFile(c *check.C) {
+	d := s.AddDaemon(c, true, true)
+
+	testFile, err := ioutil.TempFile("", "secretCreateTest")
+	c.Assert(err, checker.IsNil, check.Commentf("failed to create temporary file"))
+	defer os.Remove(testFile.Name())
+
+	testData := "TESTINGDATA"
+	_, err = testFile.Write([]byte(testData))
+	c.Assert(err, checker.IsNil, check.Commentf("failed to write to temporary file"))
+
+	testName := "test_secret"
+	out, err := d.Cmd("secret", "create", "--file", testFile.Name(), testName)
+	c.Assert(err, checker.IsNil)
+	c.Assert(strings.TrimSpace(out), checker.Not(checker.Equals), "", check.Commentf(out))
+
+	id := strings.TrimSpace(out)
+	secret := d.GetSecret(c, id)
+	c.Assert(secret.Spec.Name, checker.Equals, testName)
+
+	testName = "test_secret_2"
+	out, err = d.Cmd("secret", "create", testName, "-f", testFile.Name())
+	c.Assert(err, checker.IsNil)
+	c.Assert(strings.TrimSpace(out), checker.Not(checker.Equals), "", check.Commentf(out))
+
+	id = strings.TrimSpace(out)
+	secret = d.GetSecret(c, id)
+	c.Assert(secret.Spec.Name, checker.Equals, testName)
+}