Skip "Ping npm registry" task when using --no-publish (#226)

lib/prerequisite.js

@@ -12,15 +12,15 @@ module.exports = (input, pkg, opts) => {
 	const tasks = [
 		{
 			title: 'Ping npm registry',
-			skip: () => pkg.private || isExternalRegistry,
+			skip: () => pkg.private || isExternalRegistry || !opts.publish,
 			task: () => pTimeout(execa.stdout('npm', ['ping'])
 				.catch(() => {
 					throw new Error('Connection to npm registry failed');
 				}), 15000, 'Connection to npm registry timed out')
 		},
 		{
 			title: 'Verify user is authenticated',
-			skip: () => process.env.NODE_ENV === 'test' || pkg.private || isExternalRegistry,
+			skip: () => process.env.NODE_ENV === 'test' || pkg.private || isExternalRegistry || !opts.publish,
 			task: () => execa.stdout('npm', ['whoami'])
 				.catch(err => {
 					throw new Error(/ENEEDAUTH/.test(err.stderr) ?
@@ -70,7 +70,7 @@ module.exports = (input, pkg, opts) => {
 		},
 		{
 			title: 'Check npm version',
-			skip: () => version.isVersionLower('6.0.0', process.version),
+			skip: () => version.isVersionLower('6.0.0', process.version) || !opts.publish,
 			task: () => execa.stdout('npm', ['version', '--json']).then(json => {
 				const versions = JSON.parse(json);
 				if (!version.satisfies(versions.npm, '>=2.15.8 <3.0.0 || >=3.10.1')) {