completion: zsh: fix for directories with spaces

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.zsh

@@ -35,7 +35,7 @@ if [ -z "$script" ]; then
 	local -a locations
 	local e
 	locations=(
-		$(dirname ${funcsourcetrace[1]%:*})/git-completion.bash
+		"$(dirname ${funcsourcetrace[1]%:*})"/git-completion.bash
 		'/etc/bash_completion.d/git' # fedora, old debian
 		'/usr/share/bash-completion/completions/git' # arch, ubuntu, new debian
 		'/usr/share/bash-completion/git' # gentoo