t2027: avoid using pipes

t2027: avoid using pipes

Whenever a git command is present in the upstream of a pipe, its failure
gets masked by piping. Hence we should avoid it for testing the
upstream git command. By writing out the output of the git command to
a file, we can test the exit codes of both the commands as a failure exit
code in any command is able to stop the && chain.

Signed-off-by: Prathamesh Chavan <pc44800@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>