lib: avoid duplicate inclusion

lib/helpers.bash

@@ -1,4 +1,13 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+#
+# A collection of reusable functions.
+
+# Avoid duplicate inclusion
+if [[ -n "${__bash_it_lib_helpers:-}" ]]
+then
+    return 0
+fi
+__bash_it_lib_helpers="loaded"
 
 BASH_IT_LOAD_PRIORITY_DEFAULT_ALIAS=${BASH_IT_LOAD_PRIORITY_DEFAULT_ALIAS:-150}
 BASH_IT_LOAD_PRIORITY_DEFAULT_PLUGIN=${BASH_IT_LOAD_PRIORITY_DEFAULT_PLUGIN:-250}

lib/search.bash

@@ -1,6 +1,13 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
 #
 # Search by Konstantin Gredeskoul «github.com/kigster»
+
+# Avoid duplicate inclusion
+if [[ -n "${__bash_it_lib_search:-}" ]]
+then
+    return 0
+fi
+__bash_it_lib_search="loaded"
 #———————————————————————————————————————————————————————————————————————————————
 # This function returns list of aliases, plugins and completions in bash-it,
 # whose name or description matches one of the search terms provided as arguments.