feat(git): use remote branches only for local detached head

If the local repository is not in a detached head state, use `git rev-parse --abbrev-ref HEAD` to determine the `branch` as it is more reliable.

Author: pvdlg

lib/git.js

@@ -17,13 +17,17 @@ function head() {
 
 function branch() {
 	try {
-		const branch = execa
-			.sync('git', ['show', '-s', '--pretty=%d', 'HEAD'])
-			.stdout.replace(/^\(|\)$/g, '')
-			.split(', ')
-			.find(branch => branch.startsWith('origin/'));
+		const headRef = execa.sync('git', ['rev-parse', '--abbrev-ref', 'HEAD']).stdout;
 
-		return branch ? branch.match(/^origin\/(.+)/)[1] : execa.sync('git', ['rev-parse', '--abbrev-ref', 'HEAD']).stdout;
+		if (headRef === 'HEAD') {
+			const branch = execa
+				.sync('git', ['show', '-s', '--pretty=%d', 'HEAD'])
+				.stdout.replace(/^\(|\)$/g, '')
+				.split(', ')
+				.find(branch => branch.startsWith('origin/'));
+			return branch ? branch.match(/^origin\/(.+)/)[1] : undefined;
+		}
+		return headRef;
 	} catch (err) {
 		return undefined;
 	}

test/git.test.js

@@ -1,6 +1,6 @@
 import test from 'ava';
 import git from '../lib/git';
-import {gitRepo, gitCommit, gitHead} from './helpers/git-utils';
+import {gitRepo, gitCommit, gitHead, gitCheckout} from './helpers/git-utils';
 
 // Save the current working diretory
 const cwd = process.cwd();
@@ -17,8 +17,15 @@ test.serial('Git repository', async t => {
 	t.deepEqual(git.configuration(), {commit, branch: 'master'});
 });
 
+test.serial('Git cloned repository', async t => {
+	await gitRepo(true);
+
+	t.deepEqual(git.configuration(), {commit: await gitHead(), branch: 'master'});
+});
+
 test.serial('Git repository with detached head', async t => {
 	await gitRepo(true);
+	await gitCheckout('HEAD~0', false);
 
 	t.deepEqual(git.configuration(), {commit: await gitHead(), branch: 'master'});
 });