refactor: improve bash code (#125)

* refactor: extract guard_path to utils/guard_path.sh

* add utils/guard_operation.sh

utils/guard_operation.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+
+# Guard an operation with a confirmation prompt.
+
+main() {
+    if [ -t 1 ]; then
+        confirmation_prompt="${1:-"Are you sure you want to continue?"}"
+        read -r -p "$confirmation_prompt [Y/n] " ans
+        if [[ "$ans" == "N" || "$ans" == "n" ]]; then
+            echo "error: aborted!" 2>&1
+            exit 1
+        fi
+    fi
+}
+
+main "$@"