tests: change "cd ... && git fetch" to "cd &&\n\tgit fetch"

tests: change "cd ... && git fetch" to "cd &&\n\tgit fetch"

Change occurrences "cd" followed by "fetch" on a single line to be on
two lines.

This is purely a stylistic change pointed out in code review for an
unrelated patch. Change the these tests use so new tests added later
using the more common style don't look out of place.

Signed-off-by: Ævar Arnfjörð Bjarmason <redacted>
Signed-off-by: Junio C Hamano <redacted>