diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 66420e9ac..2b4160810 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -6,6 +6,10 @@ This project started as a little excuse to exercise some of the cool new C++11 f
 
 To make it as easy as possible for you to contribute and for me to keep an overview, here are a few guidelines which should help us avoid all kinds of unnecessary work or disappointment. And of course, this document is subject to discussion, so please [create an issue](https://github.com/nlohmann/json/issues/new) or a pull request if you find a way to improve it!
 
+## Private reports
+
+Usually, all issues are tracked publicly on [Github](https://github.com/nlohmann/json/issues). If you want to make a private report (e.g., for a vulnerability or to attach an example that is not meant to be publisheed), please send an email to <mail@nlohmann.me>.
+
 ## Prerequisites
 
 Please [create an issue](https://github.com/nlohmann/json/issues/new), assuming one does not already exist, and describe your concern. Note you need a [GitHub account](https://github.com/signup/free) for this.
@@ -57,6 +61,7 @@ Please understand that I cannot accept pull requests changing only file `src/jso
 ## Note
 
 - If you open a pull request, the code will be automatically tested with [Valgrind](http://valgrind.org)'s Memcheck tool to detect memory leaks. Please be aware that the execution with Valgrind _may_ in rare cases yield different behavior than running the code directly. This can result in failing unit tests which run successfully without Valgrind.
+- There is a Makefile target `make pretty` which runs [Artistic Style](http://astyle.sourceforge.net) to fix indentation. If possible, run it before opening the pull request. Otherwise, we shall run it afterward.
 
 ## Please don't
 
diff --git a/README.md b/README.md
index de70912b4..73a03363b 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,7 @@
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/nlohmann/json/master/LICENSE.MIT)
 [![Github Releases](https://img.shields.io/github/release/nlohmann/json.svg)](https://github.com/nlohmann/json/releases)
 [![Github Issues](https://img.shields.io/github/issues/nlohmann/json.svg)](http://github.com/nlohmann/json/issues)
+[![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/289/badge)](https://bestpractices.coreinfrastructure.org/projects/289)
 
 ## Design goals
 
diff --git a/src/json.hpp b/src/json.hpp
index 5ab8ec264..ddf37eb2e 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -9484,7 +9484,7 @@ basic_json_parser_63:
         }
 
         /// split the string input to reference tokens
-        static std::vector<std::string> split(std::string reference_string)
+        static std::vector<std::string> split(const std::string& reference_string)
         {
             std::vector<std::string> result;
 
@@ -10212,7 +10212,7 @@ basic_json_parser_63:
     */
     static basic_json diff(const basic_json& source,
                            const basic_json& target,
-                           std::string path = "")
+                           const std::string& path = "")
     {
         // the patch
         basic_json result(value_t::array);
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index 0d8ffa155..740c768c5 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -8781,7 +8781,7 @@ class basic_json
         }
 
         /// split the string input to reference tokens
-        static std::vector<std::string> split(std::string reference_string)
+        static std::vector<std::string> split(const std::string& reference_string)
         {
             std::vector<std::string> result;
 
@@ -9509,7 +9509,7 @@ class basic_json
     */
     static basic_json diff(const basic_json& source,
                            const basic_json& target,
-                           std::string path = "")
+                           const std::string& path = "")
     {
         // the patch
         basic_json result(value_t::array);