Fix command injection

Add `--` in some commands that receive user input
and if interpreted as options could lead to remote
code execution (RCE).

There may be more commands that could benefit from `--`
so the input is never interpreted as an option,
but most of those aren't dangerous.

For anyone using GitPython and exposing any of the GitPython methods to users,
make sure to always validate the input (like if starts with `--`).
And for anyone allowing users to pass arbitrary options, be aware
that some options may lead fo RCE, like `--exc`, `--upload-pack`,
`--receive-pack`, `--config` (gitpython-developers#1516).

Ref gitpython-developers#1517

Author: stsewd

git/remote.py

@@ -964,7 +964,7 @@ def fetch(
             args = [refspec]
 
         proc = self.repo.git.fetch(
-            self, *args, as_process=True, with_stdout=False, universal_newlines=True, v=verbose, **kwargs
+            '--', self, *args, as_process=True, with_stdout=False, universal_newlines=True, v=verbose, **kwargs
         )
         res = self._get_fetch_info_from_stderr(proc, progress, kill_after_timeout=kill_after_timeout)
         if hasattr(self.repo.odb, "update_cache"):
@@ -991,7 +991,7 @@ def pull(
             self._assert_refspec()
         kwargs = add_progress(kwargs, self.repo.git, progress)
         proc = self.repo.git.pull(
-            self, refspec, with_stdout=False, as_process=True, universal_newlines=True, v=True, **kwargs
+            '--', self, refspec, with_stdout=False, as_process=True, universal_newlines=True, v=True, **kwargs
         )
         res = self._get_fetch_info_from_stderr(proc, progress, kill_after_timeout=kill_after_timeout)
         if hasattr(self.repo.odb, "update_cache"):
@@ -1034,6 +1034,7 @@ def push(
             be 0."""
         kwargs = add_progress(kwargs, self.repo.git, progress)
         proc = self.repo.git.push(
+            '--',
             self,
             refspec,
             porcelain=True,

git/repo/base.py

@@ -1169,6 +1169,7 @@ def _clone(
             multi = shlex.split(" ".join(multi_options))
         proc = git.clone(
             multi,
+            "--",
             Git.polish_url(str(url)),
             clone_path,
             with_extended_output=True,
@@ -1305,7 +1306,7 @@ def archive(
         if not isinstance(path, (tuple, list)):
             path = [path]
         # end assure paths is list
-        self.git.archive(treeish, *path, **kwargs)
+        self.git.archive('--', treeish, *path, **kwargs)
         return self
 
     def has_separate_working_tree(self) -> bool: