Gracefully handle branch not having an upstream (#321)

Fixes #90

index.js

@@ -15,6 +15,7 @@ const pkgDir = require('pkg-dir');
 const prerequisiteTasks = require('./lib/prerequisite');
 const gitTasks = require('./lib/git');
 const util = require('./lib/util');
+const {hasUpstream} = require('./lib/git-util');
 const publish = require('./lib/publish');
 
 const exec = (cmd, args) => {
@@ -149,6 +150,7 @@ module.exports = async (input = 'patch', options) => {
 
 	tasks.add({
 		title: 'Pushing tags',
+		skip: async () => !(await hasUpstream()),
 		task: () => exec('git', ['push', '--follow-tags'])
 	});
 

lib/git-util.js

@@ -0,0 +1,7 @@
+'use strict';
+const execa = require('execa');
+
+exports.hasUpstream = async () => {
+	const {stdout} = await execa('git', ['status', '--short', '--branch', '--porcelain=2']);
+	return /^# branch\.upstream [\w\-/]+$/m.test(stdout);
+};

lib/git.js

@@ -25,8 +25,12 @@ module.exports = options => {
 		{
 			title: 'Check remote history',
 			task: async () => {
-				const {stdout} = await execa('git', ['rev-list', '--count', '--left-only', '@{u}...HEAD']);
-				if (stdout !== '0') {
+				let stdout;
+				try { // Gracefully handle no remote set up.
+					stdout = await execa.stdout('git', ['rev-list', '--count', '--left-only', '@{u}...HEAD']);
+				} catch (_) {}
+
+				if (stdout && stdout !== '0') {
 					throw new Error('Remote history differs. Please pull changes.');
 				}
 			}