t: wrap complicated expect_code users in a block

t: wrap complicated expect_code users in a block

If we are expecting a command to produce a particular exit
code, we can use test_expect_code. However, some cases are
more complicated, and want to accept one of a range of exit
codes. For these, we end up with something like:

  cmd;
  case "$?" in
  ...

That unfortunately breaks the &&-chain and fools
--chain-lint. Since these special cases are so few, we can
wrap them in a block, like this:

  { cmd; ret=$?; } &&
  case "$ret" in
  ...

This accomplishes the same thing, and retains the &&-chain
(the exit status fed to the && is that of the assignment,
which should always be true). It's technically longer, but
it is probably a good thing for unusual code like this to
stand out.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>