Fix storing URLs without scheme (#72)

* Fix storing URLs without scheme

If secrets are stored without specifying a scheme
(https://), the keychain-helper would interpret the
hostname as _path_, causing lookup of secrets to fail.

This patch makes sure that a scheme is added (if missing).

If no scheme is specified, https:// is used as a default.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

* Have pre go1.8 compiler able to compile

Signed-off-by: Tibor Vass <teabee89@gmail.com>

* Fix URL parsing with port and no scheme

Signed-off-by: Nassim 'Nass' Eddequiouaq <eddequiouaq.nassim@gmail.com>

* Improve parseURL comment

Signed-off-by: Nassim 'Nass' Eddequiouaq <eddequiouaq.nassim@gmail.com>

credentials/credentials_test.go

@@ -76,8 +76,8 @@ func TestStore(t *testing.T) {
 func TestStoreMissingServerURL(t *testing.T) {
 	creds := &Credentials{
 		ServerURL: "",
-		Username: "foo",
-		Secret: "bar",
+		Username:  "foo",
+		Secret:    "bar",
 	}
 
 	b, err := json.Marshal(creds)
@@ -96,8 +96,8 @@ func TestStoreMissingServerURL(t *testing.T) {
 func TestStoreMissingUsername(t *testing.T) {
 	creds := &Credentials{
 		ServerURL: "https://index.docker.io/v1/",
-		Username: "",
-		Secret: "bar",
+		Username:  "",
+		Secret:    "bar",
 	}
 
 	b, err := json.Marshal(creds)

credentials/error.go

@@ -8,7 +8,7 @@ const (
 	// ErrCredentialsMissingServerURL and ErrCredentialsMissingUsername standardize
 	// invalid credentials or credentials management operations
 	errCredentialsMissingServerURLMessage = "no credentials server URL"
-	errCredentialsMissingUsernameMessage = "no credentials username"
+	errCredentialsMissingUsernameMessage  = "no credentials username"
 )
 
 // errCredentialsNotFound represents an error
@@ -43,7 +43,6 @@ func IsErrCredentialsNotFoundMessage(err string) bool {
 	return err == errCredentialsNotFoundMessage
 }
 
-
 // errCredentialsMissingServerURL represents an error raised
 // when the credentials object has no server URL or when no
 // server URL is provided to a credentials operation requiring
@@ -64,7 +63,6 @@ func (errCredentialsMissingUsername) Error() string {
 	return errCredentialsMissingUsernameMessage
 }
 
-
 // NewErrCredentialsMissingServerURL creates a new error for
 // errCredentialsMissingServerURL.
 func NewErrCredentialsMissingServerURL() error {
@@ -77,7 +75,6 @@ func NewErrCredentialsMissingUsername() error {
 	return errCredentialsMissingUsername{}
 }
 
-
 // IsCredentialsMissingServerURL returns true if the error
 // was an errCredentialsMissingServerURL.
 func IsCredentialsMissingServerURL(err error) bool {