fix(repository): dereference reflog identity correctly

Since its introduction in commit 81520c9 (Update to libgit2 v0.23),
the reflog identity getter (Repository.ident) has been
passing the (char **) variables directly to ffi.string()
as C-strings, when they really are pointers to C-strings.
Fix by dereferencing the pointer to a C-string first.

Furthermore, Repository.ident assumes that libgit2 holds
a valid C-string, when the reflog identity is initialized
to NULL, and can be explicitly set to such with `set_ident
(None, None)`.  So map None to ffi.NULL (which maybe_string()
happens to already do, so I simply delegated to that...).

I also added a few regression tests to ensure neither issue
shows up again.

Signed-off-by: Ethan Meng <ethan@rapidcow.org>

Author: rapidcow

pygit2/repository.py

@@ -81,7 +81,7 @@
 from .remotes import RemoteCollection
 from .submodules import SubmoduleCollection
 from .transaction import ReferenceTransaction
-from .utils import StrArray, to_bytes
+from .utils import StrArray, maybe_string, to_bytes
 
 if TYPE_CHECKING:
     from pygit2._libgit2.ffi import (
@@ -1585,7 +1585,7 @@ def ident(self):
         err = C.git_repository_ident(cname, cemail, self._repo)
         check_error(err)
 
-        return (ffi.string(cname).decode('utf-8'), ffi.string(cemail).decode('utf-8'))
+        return (maybe_string(cname[0]), maybe_string(cemail[0]))
 
     def set_ident(self, name: str, email: str) -> None:
         """Set the identity to be used for reference operations.

test/test_repository.py

@@ -641,6 +641,19 @@ def test_default_signature(testrepo: Repository) -> None:
     assert 'rjh@example.com' == sig.email
 
 
+def test_ident_get_set(testrepo: Repository) -> None:
+    # By default, reflog identity should be unset.
+    assert testrepo.ident == (None, None)
+
+    cname = 'C O Mitter'
+    cemail = 'committer@example.com'
+    testrepo.set_ident(cname, cemail)
+    assert testrepo.ident == (cname, cemail)
+
+    testrepo.set_ident(None, None)
+    assert testrepo.ident == (None, None)
+
+
 def test_new_repo(tmp_path: Path) -> None:
     repo = init_repository(tmp_path, False)