As pointed out by Junio on the mailing list, surrounding tests in
double quotes can lead to bugs wherein variables get substituted away,
so this isn't just style churn but important to prevent others from
looking at these tests in the future and thinking that this is "the
way" that Git tests should be written.
Signed-off-by: Wincent Colaiuta <win@wincent.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>