credentials: use more ducks

Instead of making everyone inherit from our credential types, use an
interface with two attributes, which makes the C code much shorter and
simpler.

Author: carlosmn

pygit2/credentials.py

@@ -26,27 +26,52 @@
 # Boston, MA 02110-1301, USA.
 
 # Import from pygit2
-from _pygit2 import CredUsernamePassword, CredSshKey
-from _pygit2 import GIT_CREDTYPE_USERPASS_PLAINTEXT
+from _pygit2 import GIT_CREDTYPE_USERPASS_PLAINTEXT, GIT_CREDTYPE_SSH_KEY
 
-class UserPass(CredUsernamePassword):
+class UserPass:
     """Username/Password credentials
 
     This is an object suitable for passing to a remote's credentials
     callback and for returning from said callback.
 
     """
 
+    def __init__(self, username, password):
+        self._username = username
+        self._password = password
+
+    @property
+    def credential_type(self):
+        return GIT_CREDTYPE_USERPASS_PLAINTEXT
+
+    @property
+    def credential_tuple(self):
+        return (self._username, self._password)
+
     def __call__(self, _url, _username, _allowed):
         return self
 
-class Keypair(CredSshKey):
+class Keypair:
     """SSH key pair credentials
 
     This is an object suitable for passing to a remote's credentials
     callback and for returning from said callback.
 
     """
 
+    def __init__(self, username, pubkey, privkey, passphrase):
+        self._username = username
+        self._pubkey = pubkey
+        self._privkey = privkey
+        self._passphrase = passphrase
+
+    @property
+    def credential_type(self):
+        return GIT_CREDTYPE_SSH_KEY
+
+    @property
+    def credential_tuple(self):
+        return (self._username, self._pubkey, self._privkey, self._passphrase)
+
     def __call__(self, _url, _username, _allowed):
         return self

src/credentials.c

@@ -74,8 +74,6 @@ extern PyTypeObject RefLogEntryType;
 extern PyTypeObject BranchType;
 extern PyTypeObject SignatureType;
 extern PyTypeObject RemoteType;
-extern PyTypeObject CredUsernamePasswordType;
-extern PyTypeObject CredSshKeyType;
 extern PyTypeObject RefspecType;
 extern PyTypeObject TransferProgressType;
 extern PyTypeObject NoteType;
@@ -460,13 +458,9 @@ moduleinit(PyObject* m)
 
     /* Remotes */
     INIT_TYPE(RemoteType, NULL, NULL)
-    INIT_TYPE(CredUsernamePasswordType, NULL, PyType_GenericNew)
-    INIT_TYPE(CredSshKeyType, NULL, PyType_GenericNew)
     INIT_TYPE(RefspecType, NULL, NULL)
     INIT_TYPE(TransferProgressType, NULL, NULL)
     ADD_TYPE(m, Remote)
-    ADD_TYPE(m, CredUsernamePassword)
-    ADD_TYPE(m, CredSshKey)
     ADD_TYPE(m, Refspec)
     ADD_TYPE(m, TransferProgress)
     /* Direction for the refspec */

src/pygit2.c

@@ -39,8 +39,6 @@
 extern PyObject *GitError;
 extern PyTypeObject RepositoryType;
 extern PyTypeObject TransferProgressType;
-extern PyTypeObject CredUsernamePasswordType;
-extern PyTypeObject CredSshKeyType;
 
 PyObject *
 wrap_transfer_progress(const git_transfer_progress *stats)

src/remote.c

@@ -207,25 +207,6 @@ typedef struct {
     PyObject *update_tips;
 } Remote;
 
-typedef struct {
-    PyObject_HEAD
-    git_credtype_t credtype;
-} Cred;
-
-typedef struct {
-    Cred parent;
-    char *username;
-    char *password;
-} CredUsernamePassword;
-
-typedef struct {
-    Cred parent;
-    char *username;
-    char *pubkey;
-    char *privkey;
-    char *passphrase;
-} CredSshKey;
-
 /* git_refspec */
 typedef struct {
     PyObject_HEAD