diff --git a/Dockerfile b/Dockerfile
index e7ac5b4..777e166 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,6 +1,6 @@
 FROM apache/airflow:1.10.10-python3.7
 
 COPY entrypoint.sh /entrypoint.sh
-COPY main.py /main.py
+COPY dump_dags.py /dump_dags.py
 
 ENTRYPOINT ["/entrypoint.sh"]
diff --git a/action.yml b/action.yml
index f35fb9d..921d852 100644
--- a/action.yml
+++ b/action.yml
@@ -1,5 +1,8 @@
 name: 'Diff Airflow DAG'
 description: 'Gets diff of airflow DAG.'
+outputs:
+  diff:
+    description: 'The diff of the DAGs.'
 runs:
   using: 'docker'
   image: 'Dockerfile'
diff --git a/main.py b/dump_dags.py
similarity index 81%
rename from main.py
rename to dump_dags.py
index b6a3453..7b20969 100644
--- a/main.py
+++ b/dump_dags.py
@@ -23,4 +23,8 @@ def dump_dags(outfile):
 
 
 if __name__ == '__main__':
-    dump_dags(sys.stdout)
+    if len(sys.argv) != 2:
+        print('Usage: dump_dags.py <output filename>')
+        sys.exit(1)
+    with open(sys.argv[1], 'w') as outfile:
+        dump_dags(outfile)
diff --git a/entrypoint.sh b/entrypoint.sh
index cef4983..f3f5eb4 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -6,6 +6,9 @@ export AIRFLOW__CORE__DAGS_FOLDER=${GITHUB_WORKSPACE}/
 export AIRFLOW__CORE__PLUGINS_FOLDER=${GITHUB_WORKSPACE}/plugins/
 export AIRFLOW__CORE__LOGS_FOLDER="/tmp/logs/"
 export FERNET_KEY=$(openssl rand -base64 32)
-cat $GITHUB_EVENT_PATH
+echo Base ref is $GITHUB_BASE_REF
 airflow initdb
-python /main.py
+python /dump_dags.py /tmp/current.txt
+git checkout $GITHUB_BASE_REF
+python /dump_dags.py /tmp/base.txt
+diff=$(diff -u /tmp/base.txt /tmp/current.txt)