refactor(check): simplify code

Author: bearomorphism

commitizen/commands/check.py

@@ -103,9 +103,7 @@ def _get_commits(self):
             return [git.GitCommit(rev="", title="", body=msg)]
 
         # Get commit messages from git log (--rev-range)
-        if self.rev_range:
-            return git.get_commits(end=self.rev_range)
-        return git.get_commits()
+        return git.get_commits(end=self.rev_range or "HEAD")
 
     @staticmethod
     def _filter_comments(msg: str) -> str: