service create/update doesn't detect single-value advanced syntax

[thaJeztah]

Description

The --secret and --config flags accept both a "basic" and "advanced" (csv / option=value) syntax.

Docker fails to detect the "advanced" syntax if there is no comma in the options passed, and as a result, attempts to use option=value as name for the secret.

Describe the results you received:

1. Create a config and a secret:

   echo hello | docker config create myconfig -
   echo hello | docker secret create mysecret -

2. Create a service that uses the config, using the advanced ("csv" / "option=value") syntax

   docker service create --name hello1 --config source=myconfig nginx:alpine
   
   config not found: source=myconfig

3. Create a service that uses the secret, using the advanced ("csv" / "option=value") syntax

   docker service create --name hello2 --secret source=mysecret nginx:alpine
   
   secret not found: source=mysecret

4. Create a service that uses the config, using the "basic" syntax (just referencing the name)

   docker service create --name hello3 --config myconfig nginx:alpine
   
   08oc61ewfwbkxmasstkgv5yzw
   overall progress: 1 out of 1 tasks 
   1/1: running   [==================================================>] 
   verify: Service converged 

5. Create a service that uses the config, using the "basic" syntax (just referencing the name)

   docker service create --name hello4 --secret mysecret nginx:alpine
   
   k0fki16c5anjsylywuc75xxy1
   overall progress: 1 out of 1 tasks 
   1/1: running   [==================================================>] 
   verify: Service converged 

Describe the results you expected:

Both --secret mysecret and --secret source=mysecret should work

Secret (and config) names are restricted to [a-zA-Z0-9-_.], so --secret source=blabla should not be ambiguous

echo blabla | docker secret create source=blabla -
Error response from daemon: rpc error: code = InvalidArgument desc = invalid name, only 64 [a-zA-Z0-9-_.] characters allowed, and the start and end character must be [a-zA-Z0-9]

Proposed fix

In the "single value" case, check if the value contains a =, and if that's the case, don't return early

Parsing for secrets:

cli/opts/secret.go

Lines 34 to 40 in ae16187

	// support a simple syntax of --secret foo
	if len(fields) == 1 {
	options.File.Name = fields[0]
	options.SecretName = fields[0]
	o.values = append(o.values, options)
	return nil
	}

Parsing for configs:

cli/opts/config.go

Lines 34 to 40 in ae16187

	// support a simple syntax of --config foo
	if len(fields) == 1 {
	options.File.Name = fields[0]
	options.ConfigName = fields[0]
	o.values = append(o.values, options)
	return nil
	}

We should also check other flags that accept both "basic" and "advanced" syntax, to see if they have similar issues

Output of docker version:

Client: Docker Engine - Community
 Version:           19.03.1
 API version:       1.40
 Go version:        go1.12.5
 Git commit:        74b1e89
 Built:             Thu Jul 25 21:18:17 2019
 OS/Arch:           darwin/amd64
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          19.03.1
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.12.5
  Git commit:       74b1e89
  Built:            Thu Jul 25 21:17:52 2019
  OS/Arch:          linux/amd64
  Experimental:     true
 containerd:
  Version:          v1.2.6
  GitCommit:        894b81a4b802e4eb2a91d1ce216b8817763c29fb
 runc:
  Version:          1.0.0-rc8
  GitCommit:        425e105d5a03fabd737a126ad93d62a9eeede87f
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683