fix: CG-12266 Logging for Empty Repos + Allow Codebase Parse (#904)

- Branch checked out to main on empty repos, however, no commits exist.
In this case, parse the repo but log that no commits exist

---------

Co-authored-by: Christine Wang <[email protected]>

Author: tawsifkamal

src/codegen/git/repo_operator/repo_operator.py

@@ -166,8 +166,14 @@ def git_cli(self) -> GitCLI:
         return git_cli
 
     @property
-    def head_commit(self) -> GitCommit:
-        return self.git_cli.head.commit
+    def head_commit(self) -> GitCommit | None:
+        try:
+            return self.git_cli.head.commit
+        except ValueError as e:
+            if (f"Reference at {self.git_cli.head.ref.path!r} does not exist") in str(e):
+                logger.info(f"Ref: {self.git_cli.head.ref.name} has no commits")
+                return None
+            raise
 
     @property
     def git_diff(self) -> str:

src/codegen/sdk/core/codebase.py

@@ -898,6 +898,10 @@ def checkout(
             result = self._op.checkout_commit(commit_hash=commit)
         if result == CheckoutResult.SUCCESS:
             logger.info(f"Checked out {branch or commit}")
+            if self._op.head_commit is None:
+                logger.info(f"Ref: {self._op.git_cli.head.ref.name} has no commits")
+                return CheckoutResult.SUCCESS
+
             self.sync_to_commit(self._op.head_commit)
         elif result == CheckoutResult.NOT_FOUND:
             logger.info(f"Could not find branch {branch or commit}")
@@ -1435,6 +1439,7 @@ def from_string(
 
         with tempfile.TemporaryDirectory(prefix="codegen_") as tmp_dir:
             logger.info(f"Using directory: {tmp_dir}")
+
             codebase = CodebaseFactory.get_codebase_from_files(repo_path=tmp_dir, files=files, programming_language=prog_lang)
             logger.info("Codebase initialization complete")
             return codebase