feat(add-git-folder): validate branch before adding submodule

- Check if the target repository is on the expected branch before proceeding
- Exit with error if branch mismatch is detected
- Improve reliability of submodule addition by enforcing branch consistency

bin/add-git-folder

@@ -17,8 +17,11 @@ add-git-folder() {
     local branch="$2"
     local path="$3"
 
-    # Clone the repo
-    git clone -b "$branch" "$url" "$path"
+    local current_branch=$(git -C "$path" rev-parse --abbrev-ref HEAD)
+    if [[ "$current_branch" != "$branch" ]]; then
+        echo "Error: Repository is on branch '$current_branch', expected '$branch'"
+        exit 1
+    fi
 
     # Add entry to .gitmodules
     git config -f .gitmodules submodule."$path".path "$path"