[data] fix gemma2 eos token (#8480)

Co-authored-by: Yaowei Zheng <hiyouga@buaa.edu.cn>

src/llamafactory/data/template.py

@@ -951,6 +951,22 @@ register_template(
 )
 
 
+# copied from gemma template
+register_template(
+    name="gemma2",
+    format_user=StringFormatter(slots=["<start_of_turn>user\n{{content}}<end_of_turn>\n<start_of_turn>model\n"]),
+    format_assistant=StringFormatter(slots=["{{content}}<end_of_turn>\n"]),
+    format_system=StringFormatter(slots=["{{content}}\n\n"]),
+    format_observation=StringFormatter(
+        slots=["<start_of_turn>tool\n{{content}}<end_of_turn>\n<start_of_turn>model\n"]
+    ),
+    format_prefix=EmptyFormatter(slots=[{"bos_token"}]),
+    stop_words=["<eos>", "<end_of_turn>"],
+    efficient_eos=True,
+    template_class=Llama2Template,
+)
+
+
 # copied from gemma template
 register_template(
     name="gemma3",

src/llamafactory/extras/constants.py

@@ -712,6 +712,13 @@ register_model_group(
         "Gemma-1.1-7B-Instruct": {
             DownloadSource.DEFAULT: "google/gemma-1.1-7b-it",
         },
+    },
+    template="gemma",
+)
+
+
+register_model_group(
+    models={
         "Gemma-2-2B": {
             DownloadSource.DEFAULT: "google/gemma-2-2b",
             DownloadSource.MODELSCOPE: "LLM-Research/gemma-2-2b",
@@ -751,7 +758,7 @@ register_model_group(
             DownloadSource.MODELSCOPE: "google/medgemma-27b-text-it",
         },
     },
-    template="gemma",
+    template="gemma2",
 )