From f649587d51491eb8a86407ef5edeea89a9e740a1 Mon Sep 17 00:00:00 2001
From: Mike McQuaid <mike@mikemcquaid.com>
Date: Thu, 26 Jun 2025 12:11:11 +0100
Subject: [PATCH] cmd/update: improve Homebrew/brew `main` migration.

Let's avoid people sticking on the `master` branch unnecessarily.
---
 Library/Homebrew/cmd/update.sh | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/Library/Homebrew/cmd/update.sh b/Library/Homebrew/cmd/update.sh
index 21bea55af7..a903dd1838 100644
--- a/Library/Homebrew/cmd/update.sh
+++ b/Library/Homebrew/cmd/update.sh
@@ -252,6 +252,14 @@ EOS
   fi
 
   INITIAL_BRANCH="$(git symbolic-ref --short HEAD 2>/dev/null)"
+  if [[ "${INITIAL_BRANCH}" == "master" &&
+        ("${DIR}" == "${HOMEBREW_REPOSITORY}" || "${DIR}" == "${HOMEBREW_CASK_REPOSITORY}") ]]
+  then
+    # Migrate master to main for Homebrew/brew or Homebrew/homebrew-cask
+    INITIAL_BRANCH="main"
+    SOFT_DELETE_MASTER="1"
+  fi
+
   if [[ -n "${UPSTREAM_TAG}" ]] ||
      [[ "${INITIAL_BRANCH}" != "${UPSTREAM_BRANCH}" && -n "${INITIAL_BRANCH}" ]]
   then
@@ -328,6 +336,11 @@ EOS
     pop_stash_message
   fi
 
+  if [[ "${SOFT_DELETE_MASTER}" == 1 && -n "$(git config branch.main.remote 2>/dev/null || true)" ]]
+  then
+    git branch -d "${QUIET_ARGS[@]}" master
+  fi
+
   trap - SIGINT
 }