fix: update already present repositories

Signed-off-by: Ben Selwyn-Smith <[email protected]>

src/macaron/slsa_analyzer/git_url.py

@@ -337,11 +337,27 @@ def clone_remote_repo(clone_dir: str, url: str) -> Repo | None:
             os.rmdir(clone_dir)
             logger.debug("The clone dir %s is empty. It has been deleted for cloning the repo.", clone_dir)
         except OSError:
-            logger.debug(
-                "The clone dir %s is not empty. Cloning will not be proceeded.",
-                clone_dir,
-            )
-            return None
+            # If the repository has already been cloned, we attempt to update using `git pull`.
+            try:
+                git_env_patch = {
+                    # Setting the GIT_TERMINAL_PROMPT environment variable to ``0`` stops
+                    # ``git clone`` from prompting for login credentials.
+                    "GIT_TERMINAL_PROMPT": "0",
+                }
+                subprocess.run(  # nosec B603
+                    args=["git", "pull"],
+                    capture_output=True,
+                    cwd=clone_dir,
+                    # If `check=True` and return status code is not zero, subprocess.CalledProcessError is
+                    # raised, which we don't want. We want to check the return status code of the subprocess
+                    # later on.
+                    check=False,
+                    env=get_patched_env(git_env_patch),
+                )
+                return Repo(path=clone_dir)
+            except (subprocess.CalledProcessError, OSError):
+                logger.debug("The clone dir %s is not empty. An attempt to update it failed.")
+                return None
 
     # Ensure that the parent directory where the repo is cloned into exists.
     parent_dir = Path(clone_dir).parent