From 0973b4b6c402cbb112a88eb61091c03aaaff9fc4 Mon Sep 17 00:00:00 2001
From: Benjamin Elder <bentheelder@google.com>
Date: Mon, 20 May 2024 17:05:52 -0700
Subject: [PATCH] define BRANCH to silence undefined variable warning

---
 build/root/Makefile | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/build/root/Makefile b/build/root/Makefile
index 609f3a5e709..af5239b3f7d 100644
--- a/build/root/Makefile
+++ b/build/root/Makefile
@@ -33,10 +33,12 @@ endif
 SHELL := /usr/bin/env bash -o errexit -o pipefail -o nounset
 BASH_ENV := ./hack/lib/logging.sh
 
-# Define variables so `make --warn-undefined-variables` works.
+# Define optional user-input variables so `make --warn-undefined-variables` works.
+# Usage is described below with each target that respects these
 PRINT_HELP ?=
 WHAT ?=
 TESTS ?=
+BRANCH ?=
 
 # We don't need make's built-in rules.
 MAKEFLAGS += --no-builtin-rules