Read ZDOTDIR environment variable

Library/Homebrew/test/utils/shell_spec.rb

@@ -21,13 +21,13 @@ RSpec.describe Utils::Shell do
 
     it "returns /tmp/.zshrc for Zsh if ZDOTDIR is /tmp" do
       ENV["SHELL"] = "/bin/zsh"
-      ENV["ZDOTDIR"] = "/tmp"
+      ENV["HOMEBREW_ZDOTDIR"] = "/tmp"
       expect(described_class.profile).to eq("/tmp/.zshrc")
     end
 
     it "returns ~/.zshrc for Zsh" do
       ENV["SHELL"] = "/bin/zsh"
-      ENV["ZDOTDIR"] = nil
+      ENV["HOMEBREW_ZDOTDIR"] = nil
       expect(described_class.profile).to eq("~/.zshrc")
     end
 

Library/Homebrew/utils/shell.rb

@@ -60,7 +60,7 @@ module Utils
         rc_profile = "#{Dir.home}/.rcrc"
         return rc_profile if File.exist? rc_profile
       when :zsh
-        return "#{ENV["ZDOTDIR"]}/.zshrc" if ENV["ZDOTDIR"].present?
+        return "#{ENV["HOMEBREW_ZDOTDIR"]}/.zshrc" if ENV["HOMEBREW_ZDOTDIR"].present?
       end
 
       SHELL_PROFILE_MAP.fetch(preferred, "~/.profile")

bin/brew

@@ -180,6 +180,7 @@ USED_BY_HOMEBREW_VARS=(
   TMUX
   XDG_CACHE_HOME
   XDG_RUNTIME_DIR
+  ZDOTDIR
 )
 for VAR in "${USED_BY_HOMEBREW_VARS[@]}"
 do