Add brew completion missing disclaimer

plugins/brew/brew.plugin.zsh

@@ -2,3 +2,19 @@ alias brews='brew list -1'
 alias bubo='brew update && brew outdated'
 alias bubc='brew upgrade && brew cleanup'
 alias bubu='bubo && bubc'
+
+if mkdir "$ZSH_CACHE_DIR/.brew-completion-message" 2>/dev/null; then
+	print -P '%F{yellow}'Oh My Zsh brew plugin:
+	cat <<-'EOF'
+
+		  With the advent of their 1.0 release, Homebrew has decided to bundle
+		  the zsh completion as part of the brew installation, so we no longer
+		  ship it with the brew plugin; now it only has brew aliases.
+
+		  If you find that brew completion no longer works, make sure you have
+		  your Homebrew installation fully up to date.
+
+		  You will only see this message once.
+	EOF
+	print -P '%f'
+fi