From c4422bdbb553bc3ff89a7fdfa3ceabe7cd5a49c6 Mon Sep 17 00:00:00 2001
From: Michael Bemmerl <mail@mx-server.de>
Date: Wed, 27 May 2020 21:08:06 +0000
Subject: [PATCH] [Core] Fix notice of undefined offset when in detached HEAD
 state. (#1569)

---
 lib/Configuration.php | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/lib/Configuration.php b/lib/Configuration.php
index 76a34aff..d46a6091 100644
--- a/lib/Configuration.php
+++ b/lib/Configuration.php
@@ -244,9 +244,13 @@ final class Configuration {
 		if(@is_readable($headFile)) {
 
 			$revisionHashFile = '.git/' . substr(file_get_contents($headFile), 5, -1);
-			$branchName = explode('/', $revisionHashFile)[3];
-			if(file_exists($revisionHashFile)) {
-				return 'git.' . $branchName . '.' . substr(file_get_contents($revisionHashFile), 0, 7);
+			$parts = explode('/', $revisionHashFile);
+
+			if(isset($parts[3])) {
+				$branchName = $parts[3];
+				if(file_exists($revisionHashFile)) {
+					return 'git.' . $branchName . '.' . substr(file_get_contents($revisionHashFile), 0, 7);
+				}
 			}
 		}