Add "src" alias for `--secret`

This patch adds a "src" alias for `--secret`
to be consistent with `--mount`.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 950658bbb6)
Signed-off-by: Victor Vieux <vieux@docker.com>

opts/secret.go

@@ -50,7 +50,7 @@ func (o *SecretOpt) Set(value string) error {
 
 		value := parts[1]
 		switch key {
-		case "source":
+		case "source", "src":
 			options.Source = value
 		case "target":
 			tDir, _ := filepath.Split(value)

opts/secret_test.go

@@ -35,6 +35,18 @@ func TestSecretOptionsSourceTarget(t *testing.T) {
 	assert.Equal(t, req.Target, "testing")
 }
 
+func TestSecretOptionsShorthand(t *testing.T) {
+	var opt SecretOpt
+
+	testCase := "src=foo,target=testing"
+	assert.NilError(t, opt.Set(testCase))
+
+	reqs := opt.Value()
+	assert.Equal(t, len(reqs), 1)
+	req := reqs[0]
+	assert.Equal(t, req.Source, "foo")
+}
+
 func TestSecretOptionsCustomUidGid(t *testing.T) {
 	var opt SecretOpt