diff --git a/git/objects/commit.py b/git/objects/commit.py
index 884f65228..9d7096563 100644
--- a/git/objects/commit.py
+++ b/git/objects/commit.py
@@ -128,6 +128,7 @@ def __init__(self, repo: 'Repo', binsha: bytes, tree: Union[Tree, None] = None,
             as what time.altzone returns. The sign is inverted compared to git's
             UTC timezone."""
         super(Commit, self).__init__(repo, binsha)
+        self.binsha = binsha
         if tree is not None:
             assert isinstance(tree, Tree), "Tree needs to be a Tree instance, was %s" % type(tree)
         if tree is not None:
diff --git a/git/objects/submodule/base.py b/git/objects/submodule/base.py
index 29212167c..143511909 100644
--- a/git/objects/submodule/base.py
+++ b/git/objects/submodule/base.py
@@ -563,6 +563,7 @@ def update(self, recursive: bool = False, init: bool = True, to_latest_revision:
                     progress.update(op, i, len_rmts, prefix + "Done fetching remote of submodule %r" % self.name)
                 # END fetch new data
             except InvalidGitRepositoryError:
+                mrepo = None
                 if not init:
                     return self
                 # END early abort if init is not allowed
@@ -603,7 +604,7 @@ def update(self, recursive: bool = False, init: bool = True, to_latest_revision:
 
                         # make sure HEAD is not detached
                         mrepo.head.set_reference(local_branch, logmsg="submodule: attaching head to %s" % local_branch)
-                        mrepo.head.ref.set_tracking_branch(remote_branch)
+                        mrepo.head.reference.set_tracking_branch(remote_branch)
                     except (IndexError, InvalidGitRepositoryError):
                         log.warning("Failed to checkout tracking branch %s", self.branch_path)
                     # END handle tracking branch
@@ -629,13 +630,14 @@ def update(self, recursive: bool = False, init: bool = True, to_latest_revision:
             if mrepo is not None and to_latest_revision:
                 msg_base = "Cannot update to latest revision in repository at %r as " % mrepo.working_dir
                 if not is_detached:
-                    rref = mrepo.head.ref.tracking_branch()
+                    rref = mrepo.head.reference.tracking_branch()
                     if rref is not None:
                         rcommit = rref.commit
                         binsha = rcommit.binsha
                         hexsha = rcommit.hexsha
                     else:
-                        log.error("%s a tracking branch was not set for local branch '%s'", msg_base, mrepo.head.ref)
+                        log.error("%s a tracking branch was not set for local branch '%s'",
+                                  msg_base, mrepo.head.reference)
                     # END handle remote ref
                 else:
                     log.error("%s there was no local tracking branch", msg_base)
diff --git a/git/objects/submodule/root.py b/git/objects/submodule/root.py
index bcac5419a..5e84d1616 100644
--- a/git/objects/submodule/root.py
+++ b/git/objects/submodule/root.py
@@ -2,9 +2,7 @@
     Submodule,
     UpdateProgress
 )
-from .util import (
-    find_first_remote_branch
-)
+from .util import find_first_remote_branch
 from git.exc import InvalidGitRepositoryError
 import git