add msrv badge + script to generate it (#680)

* add msrv badge + script to generate it

Signed-off-by: clux <[email protected]>

* use jq select

Signed-off-by: clux <[email protected]>

Author: clux

README.md

@@ -4,6 +4,7 @@
 [![Client Capabilities](https://img.shields.io/badge/Kubernetes%20client-Silver-blue.svg?style=plastic&colorB=C0C0C0&colorA=306CE8)](http://bit.ly/kubernetes-client-capabilities-badge)
 [![Client Support Level](https://img.shields.io/badge/kubernetes%20client-beta-green.svg?style=plastic&colorA=306CE8)](http://bit.ly/kubernetes-client-support-badge)
 [![Crates.io](https://img.shields.io/crates/v/kube.svg)](https://crates.io/crates/kube)
+[![Rust 1.56](https://img.shields.io/badge/MSRV-1.56-dea584.svg)](https://github.com/rust-lang/rust/releases/tag/1.56.0)
 [![Discord chat](https://img.shields.io/discord/500028886025895936.svg?logo=discord&style=plastic)](https://discord.gg/tokio)
 
 Rust client for [Kubernetes](http://kubernetes.io) in the style of a more generic [client-go](https://github.com/kubernetes/client-go), a runtime abstraction inspired by [controller-runtime](https://github.com/kubernetes-sigs/controller-runtime), and a derive macro for [CRDs](https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/) inspired by [kubebuilder](https://book.kubebuilder.io/reference/generating-crd.html).

scripts/msrv.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+set -euo pipefail
+
+main() {
+    local -r msrv="$(cargo msrv --output-format=json | jq -r 'select(.reason == "msrv-complete") | .msrv')"
+    local -r badge="[![Rust ${msrv::-2}](https://img.shields.io/badge/MSRV-${msrv::-2}-dea584.svg)](https://github.com/rust-lang/rust/releases/tag/${msrv})"
+    sd "^.+badge/MSRV.+$" "${badge}" README.md
+}
+
+
+# helper script to be run by users when bumping dependencies
+#
+# This script determines our msrv using cargo-msrv, and then
+# edits the badge in the README using `sd`.
+#
+# shellcheck disable=SC2068
+main $@