Add Nushell switch command

hack/switch/switch.nu

@@ -0,0 +1,70 @@
+const default_executable_path = "switcher"
+
+export def --env --wrapped main [
+    ...args
+]: nothing -> nothing {
+  let result = (switch-inner ...$args)
+  if $result.exit_code? != null {
+    return
+  }
+
+  $env.KUBECONFIG = $result.kubeconfig
+  print $"switched to context ($result.context)"
+}
+
+def --wrapped switch-inner [
+    --executable-path: path
+    ...args
+] {
+  let opts = []
+
+  let executable_path = ($executable_path | default $default_executable_path)
+
+  let response = (do {
+     ^$executable_path ...$args
+  } | complete)
+  if ($response.exit_code != 0 or ($response.stdout | str trim) == "") {
+    print $response.stdout
+    return {exit_code: $response.exit_code}
+  }
+
+  let resp_text = ($response.stdout | str trim)
+  let prefix = "__ "
+
+  if not ($resp_text | str starts-with $prefix) {
+    print $resp_text
+    return {exit_code: 0}
+  }
+
+  # Remove prefix
+  let resp_text = ($resp_text | str replace $prefix "")
+
+  # Parse out kubeconfig path and context
+  let parts = ($resp_text | split row ",")
+  if ($parts | length) != 2 {
+    error make {
+      msg: $"got an unexpected output from switcher: ($resp_text)"
+    }
+  }
+  let kubeconfig_path = ($parts | get 0)
+  let selected_context = ($parts | get 1)
+
+  if $kubeconfig_path == "" {
+    error make { msg: $resp_text }
+  }
+
+  if $selected_context == "" {
+    error make { msg: $resp_text }
+  }
+
+  # Cleanup old temporary kubeconfig file
+  let switch_tmp_directory = $"($env.HOME)/.kube/.switch_tmp/config"
+  if ($env.KUBECONFIG? != null and ($env.KUBECONFIG | str contains $switch_tmp_directory)) {
+    rm $env.KUBECONFIG
+  }
+
+  return {
+    kubeconfig: $kubeconfig_path
+    context: $selected_context
+  }
+}