Assure API remains backwards compatible; update API docs

Author: Byron

git/objects/commit.py

@@ -276,14 +276,17 @@ def create_from_tree(cls, repo, tree, message, parent_commits=None, head=False,
             If True, the HEAD will be advanced to the new commit automatically.
             Else the HEAD will remain pointing on the previous commit. This could
             lead to undesired results when diffing files.
+        :param author: The name of the author, optional. If unset, the repository 
+            configuration is used to obtain this value.
+        :param committer: The name of the committer, optional. If unset, the 
+            repository configuration is used to obtain this value.
 
         :return: Commit object representing the new commit
 
         :note:
             Additional information about the committer and Author are taken from the
             environment or from the git configuration, see git-commit-tree for
             more information"""
-        parents = parent_commits
         if parent_commits is None:
             try:
                 parent_commits = [repo.head.commit]
@@ -357,7 +360,6 @@ def create_from_tree(cls, repo, tree, message, parent_commits=None, head=False,
             except ValueError:
                 # head is not yet set to the ref our HEAD points to
                 # Happens on first commit
-                import git.refs
                 master = git.refs.Head.create(repo, repo.head.ref, new_commit, logmsg="commit (initial): %s" % message)
                 repo.head.set_reference(master, logmsg='commit: Switching to %s' % master)
             # END handle empty repositories

git/refs/symbolic.py

@@ -356,10 +356,16 @@ def log_append(self, oldbinsha, message, newbinsha=None):
             will be used
         :return: added RefLogEntry instance"""
         # NOTE: we use the committer of the currently active commit - this should be 
-        # correct. See https://github.com/gitpython-developers/GitPython/pull/146
-        return RefLog.append_entry(self.commit.committer, RefLog.path(self), oldbinsha, 
+        # correct to allow overriding the committer on a per-commit level.
+        # See https://github.com/gitpython-developers/GitPython/pull/146
+        try:
+            committer_or_reader = self.commit.committer
+        except ValueError:
+            committer_or_reader = self.repo.config_reader()
+        # end handle newly cloned repositories
+        return RefLog.append_entry(committer_or_reader, RefLog.path(self), oldbinsha, 
                                     (newbinsha is None and self.commit.binsha) or newbinsha, 
-                                    message) 
+                                    message)
 
     def log_entry(self, index):
         """:return: RefLogEntry at the given index