tag: add get_object() method

This maps to git_tag_peel().

docs/objects.rst

@@ -267,6 +267,8 @@ A tag is a static label for a commit. See references for more information.
 .. autoattribute:: pygit2.Tag.tagger
 .. autoattribute:: pygit2.Tag.message
 
+.. automethod:: pygit2.Tag.get_object
+
 
 Creating tags
 --------------------

src/tag.c

@@ -27,6 +27,7 @@
 
 #define PY_SSIZE_T_CLEAN
 #include <Python.h>
+#include "object.h"
 #include "error.h"
 #include "types.h"
 #include "utils.h"
@@ -47,6 +48,25 @@ Tag_target__get__(Tag *self)
 }
 
 
+PyDoc_STRVAR(Tag_get_object__doc__,
+  "get_object() -> object\n"
+  "\n"
+  "Retrieves the object the current reference is pointing to.");
+
+PyObject *
+Tag_get_object(Tag *self)
+{
+    int err;
+    git_object* obj;
+
+    err = git_tag_peel(&obj, self->tag);
+    if (err < 0)
+        return Error_set(err);
+
+    return wrap_object(obj, self->repo);
+}
+
+
 PyDoc_STRVAR(Tag_name__doc__, "Tag name.");
 
 PyObject *
@@ -94,6 +114,11 @@ Tag__message__get__(Tag *self)
     return PyBytes_FromString(git_tag_message(self->tag));
 }
 
+PyMethodDef Tag_methods[] = {
+    METHOD(Tag, get_object, METH_NOARGS),
+    {NULL}
+};
+
 PyGetSetDef Tag_getseters[] = {
     GETTER(Tag, target),
     GETTER(Tag, name),
@@ -134,7 +159,7 @@ PyTypeObject TagType = {
     0,                                         /* tp_weaklistoffset */
     0,                                         /* tp_iter           */
     0,                                         /* tp_iternext       */
-    0,                                         /* tp_methods        */
+    Tag_methods,                               /* tp_methods        */
     0,                                         /* tp_members        */
     Tag_getseters,                             /* tp_getset         */
     0,                                         /* tp_base           */

test/test_tag.py

@@ -89,6 +89,11 @@ class TagTest(utils.BareRepoTestCase):
         self.assertRaises(AttributeError, setattr, tag, 'tagger', tagger)
         self.assertRaises(AttributeError, setattr, tag, 'message', message)
 
+    def test_get_object(self):
+        repo = self.repo
+        tag = repo[TAG_SHA]
+        self.assertEqual(repo[tag.target].oid, tag.get_object().oid)
+
 
 if __name__ == '__main__':
     unittest.main()