Created fail_if_not_git_repo function and prepended it to all git functions

lib/git/helpers.sh

@@ -5,4 +5,12 @@ function find_in_cwd_or_parent() {
     directory="$directory/.."
   done
   return 1
+}
+
+function fail_if_not_git_repo() {
+  if ! find_in_cwd_or_parent ".git" > /dev/null; then
+    echo -e "\e[31mNot a git repository (or any of the parent directories)\e[0m"
+    return 1
+  fi
+  return 0
 }