feat(commands/commit): abort commit if there is nothing to commit

Author: Lee-W

commitizen/commands/commit.py

@@ -9,6 +9,7 @@
 NO_ANSWERS = 5
 COMMIT_ERROR = 6
 NO_COMMIT_BACKUP = 7
+NOTHING_TO_COMMIT = 8
 
 
 class Commit:
@@ -21,6 +22,10 @@ def __init__(self, config: dict, arguments: dict):
         self.temp_file: str = os.path.join(tempfile.gettempdir(), "cz.commit.backup")
 
     def __call__(self):
+        if git.is_staging_clean():
+            out.write("No files added to staging!")
+            raise SystemExit(NOTHING_TO_COMMIT)
+
         retry: bool = self.arguments.get("retry")
 
         if retry: