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.

Fixed commands:

- push
- pull
- fetch
- clone/clone_from and friends
- archive (not sure if this one can be exploited, but it doesn't hurt
  adding `--` :))

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

Diff for: 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,

Diff for: 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: