diff --git a/src/scmrepo/git/__init__.py b/src/scmrepo/git/__init__.py
index 5a9fad99..6b9265aa 100644
--- a/src/scmrepo/git/__init__.py
+++ b/src/scmrepo/git/__init__.py
@@ -22,6 +22,12 @@
 from .backend.dulwich import DulwichBackend
 from .backend.gitpython import GitPythonBackend
 from .backend.pygit2 import Pygit2Backend
+from .objects import (  # noqa: F401, pylint: disable=unused-import
+    GitCommit,
+    GitObject,
+    GitTag,
+    GitTrie,
+)
 from .stash import Stash
 
 if TYPE_CHECKING:
diff --git a/src/scmrepo/git/backend/base.py b/src/scmrepo/git/backend/base.py
index f68ee908..e0188590 100644
--- a/src/scmrepo/git/backend/base.py
+++ b/src/scmrepo/git/backend/base.py
@@ -110,7 +110,13 @@ def branch(self, branch: str):
         pass
 
     @abstractmethod
-    def tag(self, tag: str, annotated: bool = False, message: Optional[str] = None):
+    def tag(
+        self,
+        tag: str,
+        target: Optional[str] = None,
+        annotated: bool = False,
+        message: Optional[str] = None,
+    ):
         pass
 
     @abstractmethod
diff --git a/src/scmrepo/git/backend/dulwich/__init__.py b/src/scmrepo/git/backend/dulwich/__init__.py
index 4be03622..3674a14b 100644
--- a/src/scmrepo/git/backend/dulwich/__init__.py
+++ b/src/scmrepo/git/backend/dulwich/__init__.py
@@ -2,6 +2,7 @@
 import locale
 import logging
 import os
+import re
 import stat
 from contextlib import closing
 from functools import partial
@@ -390,7 +391,13 @@ def branch(self, branch: str):
         except Error as exc:
             raise SCMError(f"Failed to create branch '{branch}'") from exc
 
-    def tag(self, tag: str, annotated: bool = False, message: Optional[str] = None):
+    def tag(
+        self,
+        tag: str,
+        target: Optional[str] = None,
+        annotated: bool = False,
+        message: Optional[str] = None,
+    ):
         from dulwich.porcelain import Error, tag_create
 
         if annotated and not message:
@@ -399,6 +406,7 @@ def tag(self, tag: str, annotated: bool = False, message: Optional[str] = None):
             tag_create(
                 self.repo,
                 os.fsencode(tag),
+                objectish=target or "HEAD",
                 annotated=annotated,
                 message=message.encode("utf-8") if message else None,
             )
@@ -423,10 +431,19 @@ def active_branch(self) -> str:
         raise NotImplementedError
 
     def list_branches(self) -> Iterable[str]:
-        raise NotImplementedError
+        from dulwich.refs import LOCAL_BRANCH_PREFIX
+
+        return sorted(
+            os.fsdecode(ref[len(LOCAL_BRANCH_PREFIX) :])
+            for ref in self.repo.refs.keys()
+        )
 
     def list_tags(self) -> Iterable[str]:
-        raise NotImplementedError
+        from dulwich.refs import LOCAL_TAG_PREFIX
+
+        return sorted(
+            os.fsdecode(ref[len(LOCAL_TAG_PREFIX) :]) for ref in self.repo.refs.keys()
+        )
 
     def list_all_commits(self) -> Iterable[str]:
         raise NotImplementedError
@@ -890,12 +907,25 @@ def get_tag(self, name: str) -> Optional[Union[str, "GitTag"]]:
         if ref in self.repo and isinstance(self.repo[ref], Tag):
             tag = self.repo[ref]
             _typ, target_sha = tag.object
+            tagger_name, tagger_email = _parse_identity(tag.tagger.decode("utf-8"))
             return GitTag(
                 os.fsdecode(tag.name),
                 tag.id,
                 target_sha.decode("ascii"),
+                tagger_name,
+                tagger_email,
                 tag.tag_time,
                 tag.tag_timezone,
                 tag.message.decode("utf-8"),
             )
         return os.fsdecode(ref)
+
+
+_IDENTITY_RE = re.compile(r"(?P<name>.+)\s+<(?P<email>.+)>")
+
+
+def _parse_identity(identity: str) -> Tuple[str, str]:
+    m = _IDENTITY_RE.match(identity)
+    if not m:
+        raise SCMError("Could not parse tagger identity '{identity}'")
+    return m.group("name"), m.group("email")
diff --git a/src/scmrepo/git/backend/gitpython.py b/src/scmrepo/git/backend/gitpython.py
index 83b3ceb8..0967a478 100644
--- a/src/scmrepo/git/backend/gitpython.py
+++ b/src/scmrepo/git/backend/gitpython.py
@@ -294,10 +294,16 @@ def push(self):
     def branch(self, branch):
         self.repo.git.branch(branch)
 
-    def tag(self, tag: str, annotated: bool = False, message: Optional[str] = None):
+    def tag(
+        self,
+        tag: str,
+        target: Optional[str] = None,
+        annotated: bool = False,
+        message: Optional[str] = None,
+    ):
         if annotated and not message:
             raise SCMError("message is required for annotated tag")
-        self.repo.git.tag(tag, a=annotated, m=message)
+        self.repo.git.tag(tag, target or "HEAD", a=annotated, m=message)
 
     def untracked_files(self):
         files = self.repo.untracked_files
@@ -392,6 +398,12 @@ def resolve_commit(self, rev: str) -> "GitCommit":
             commit.committer_tz_offset,
             commit.message,
             [str(parent) for parent in commit.parents],
+            commit.committer.name,
+            commit.committer.email,
+            commit.author.name,
+            commit.author.email,
+            commit.authored_date,
+            commit.author_tz_offset,
         )
 
     def set_ref(
@@ -695,6 +707,8 @@ def get_tag(self, name: str) -> Optional[Union[str, "GitTag"]]:
                 tag.tag,
                 tag.hexsha,
                 tag.object.hexsha,
+                tag.tagger.name,
+                tag.tagger.email,
                 tag.tagged_date,
                 tag.tagger_tz_offset,
                 tag.message,
diff --git a/src/scmrepo/git/backend/pygit2/__init__.py b/src/scmrepo/git/backend/pygit2/__init__.py
index 277cc26f..f35da8a6 100644
--- a/src/scmrepo/git/backend/pygit2/__init__.py
+++ b/src/scmrepo/git/backend/pygit2/__init__.py
@@ -30,6 +30,7 @@
 
 
 if TYPE_CHECKING:
+    from pygit2 import Signature
     from pygit2.remote import Remote  # type: ignore
     from pygit2.repository import Repository
 
@@ -124,12 +125,33 @@ def _resolve_refish(self, refish: str):
         return commit, ref
 
     @property
-    def default_signature(self):
+    def default_signature(self) -> "Signature":
         try:
             return self.repo.default_signature
         except KeyError as exc:
             raise SCMError("Git username and email must be configured") from exc
 
+    @property
+    def author(self) -> "Signature":
+        return self._get_signature("GIT_AUTHOR")
+
+    @property
+    def committer(self) -> "Signature":
+        return self._get_signature("GIT_COMMITTER")
+
+    def _get_signature(self, name: str) -> "Signature":
+        from pygit2 import Signature
+
+        sig = self.default_signature
+        if os.environ.get(f"{name}_DATE"):
+            raise NotImplementedError("signature date override unsupported")
+        return Signature(
+            name=os.environ.get(f"{name}_NAME", sig.name),
+            email=os.environ.get(f"{name}_EMAIL", sig.email),
+            time=sig.time,
+            offset=sig.offset,
+        )
+
     @staticmethod
     def _get_checkout_strategy(strategy: Optional[int] = None):
         from pygit2 import (
@@ -274,17 +296,24 @@ def branch(self, branch: str):
         except GitError as exc:
             raise SCMError(f"Failed to create branch '{branch}'") from exc
 
-    def tag(self, tag: str, annotated: bool = False, message: Optional[str] = None):
+    def tag(
+        self,
+        tag: str,
+        target: Optional[str] = None,
+        annotated: bool = False,
+        message: Optional[str] = None,
+    ):
         from pygit2 import GIT_OBJ_COMMIT, GitError
 
         if annotated and not message:
             raise SCMError("message is required for annotated tag")
+        target_obj = self.repo.revparse_single(target or "HEAD")
         with reraise(GitError, SCMError("Failed to create tag")):
             self.repo.create_tag(
                 tag,
-                self.repo.head.target,
+                target_obj.id,
                 GIT_OBJ_COMMIT,
-                self.default_signature,
+                self.committer,
                 message or "",
             )
 
@@ -308,10 +337,12 @@ def active_branch(self) -> str:
         return self.repo.head.shorthand
 
     def list_branches(self) -> Iterable[str]:
-        raise NotImplementedError
+        base = "refs/heads/"
+        return sorted(ref[len(base) :] for ref in self.iter_refs(base))
 
     def list_tags(self) -> Iterable[str]:
-        raise NotImplementedError
+        base = "refs/tags/"
+        return sorted(ref[len(base) :] for ref in self.iter_refs(base))
 
     def list_all_commits(self) -> Iterable[str]:
         raise NotImplementedError
@@ -356,6 +387,12 @@ def resolve_commit(self, rev: str) -> "GitCommit":
             commit.commit_time_offset,
             commit.message,
             [str(parent) for parent in commit.parent_ids],
+            commit.committer.name,
+            commit.committer.email,
+            commit.author.name,
+            commit.author.email,
+            commit.author.time,
+            commit.author.offset,
         )
 
     def _get_stash(self, ref: str):
@@ -591,7 +628,7 @@ def _stash_push(
 
         try:
             oid = self.repo.stash(
-                self.default_signature,
+                self.committer,
                 message=message,
                 include_untracked=include_untracked,
             )
@@ -876,12 +913,11 @@ def _merge_ff(self, rev: str, obj) -> str:
     def _merge_commit(self, msg: Optional[str], obj) -> str:
         if not msg:
             raise SCMError("Merge commit message is required")
-        user = self.default_signature
         tree = self.repo.index.write_tree()
         merge_commit = self.repo.create_commit(
             "HEAD",
-            user,
-            user,
+            self.author,
+            self.committer,
             msg,
             tree,
             [self.repo.head.target, obj.id],
@@ -910,6 +946,8 @@ def get_tag(self, name: str) -> Optional[Union[str, "GitTag"]]:
                     tag.name,
                     str(tag.oid),
                     str(tag.target),
+                    tag.tagger.name,
+                    tag.tagger.email,
                     tag.tagger.time,
                     tag.tagger.offset,
                     tag.message,
diff --git a/src/scmrepo/git/objects.py b/src/scmrepo/git/objects.py
index 9cc874bd..25a0afc8 100644
--- a/src/scmrepo/git/objects.py
+++ b/src/scmrepo/git/objects.py
@@ -162,6 +162,12 @@ class GitCommit:
     commit_time_offset: int
     message: str
     parents: List[str]
+    committer_name: str
+    committer_email: str
+    author_name: str
+    author_email: str
+    author_time: int
+    author_time_offset: int
 
 
 @dataclass
@@ -169,6 +175,8 @@ class GitTag:
     name: str
     hexsha: str  # SHA for the tag object itself
     target: str  # SHA for the object the tag points to
+    tagger_name: str
+    tagger_email: str
     tag_time: int
     tag_time_offset: int
     message: str