Gábor Szeder authored Feb 24, 2018 and Junio C Hamano committed Feb 28, 2018

Three "missing reference" tests in 't5500-fetch-pack.sh' fail when the
test script is run with '-x' tracing (and using a shell other than a
Bash version supporting BASH_XTRACEFD).  The reason for those failures
is that the tests check a subshell's stderr, which includes the trace
of executing commands in that subshell as well, throwing off the
comparison with the expected output.

Save the stderr of 'git fetch-pack' only instead of the whole
subshell, so it remains free from tracing output.

After this change t5500 passes with '-x', even when running with
/bin/sh.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>