feat: add pre-commit check for internal branch

.pre-commit-config.yaml

@@ -21,6 +21,15 @@ repos:
     stages: [commit]
     language: system
     entry: jupyter nbconvert --to notebook --ClearOutputPreprocessor.enabled=True --inplace
+- repo: local
+  hooks:
+  - id: internal-is-on-main
+    name:  internal-is-on-main
+    stages: [commit]
+    language: system
+    entry: ./check_submodule_version.sh
+    always_run: true
+
 - repo: local
   hooks:
   - id: reveal_type

check_submodule_version.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+SCRIPT_DIR=$(dirname "$0")
+TARGET_DIR="$SCRIPT_DIR/zetta_utils/internal"
+
+cd $TARGET_DIR
+
+if git merge-base --is-ancestor HEAD origin/main; then
+    echo "Submodule's commit is on the main branch."
+else
+    echo "Error: Submodule's commit is not on the main branch."
+    exit 1
+fi
+
+cd -