From 942f419a48426d14a1b49d35f343cbe00a583e71 Mon Sep 17 00:00:00 2001
From: Sam Ford <1584702+samford@users.noreply.github.com>
Date: Mon, 17 Oct 2022 13:06:52 -0400
Subject: [PATCH] ResourceAuditor: Fix #audit_head_branch error

The existing logic in `#audit_head_branch` for identifying the `HEAD`
branch in a Git repository will give an ```undefined method `[]' for
nil:NilClass``` error when a repository doesn't provide this
reference. Expected output is as follows:

```
ref: refs/heads/master  HEAD
1a8f9ac700873d1a08de31a17a2fd654245d5085  HEAD
```

However, I encountered this error for a repository with the following
output (i.e., where no symref is provided for HEAD):

```
f86be659718c0cd0a67f88b42f07044c23d0d028  HEAD
```

This commit resolves the error by modifying the related logic to
account for a `nil` value.
---
 Library/Homebrew/resource_auditor.rb | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/Library/Homebrew/resource_auditor.rb b/Library/Homebrew/resource_auditor.rb
index 624f2b8e07..ac51bb0cd9 100644
--- a/Library/Homebrew/resource_auditor.rb
+++ b/Library/Homebrew/resource_auditor.rb
@@ -146,9 +146,8 @@ module Homebrew
       return if specs[:tag].present?
 
       branch = Utils.popen_read("git", "ls-remote", "--symref", url, "HEAD")
-                    .match(%r{ref: refs/heads/(.*?)\s+HEAD})[1]
-
-      return if branch == specs[:branch]
+                    .match(%r{ref: refs/heads/(.*?)\s+HEAD})&.to_a&.second
+      return if branch.blank? || branch == specs[:branch]
 
       problem "Use `branch: \"#{branch}\"` to specify the default branch"
     end