t5310-pack-bitmaps: fix bogus 'pack-objects to file can use bitmap' test

The test 'pack-objects to file can use bitmap' added in 645c432d61 (pack-objects: use reachability bitmap index when generating non-stdout pack, 2016-09-10) is silently buggy and doesn't check what it's supposed to. In 't5310-pack-bitmaps.sh', the 'list_packed_objects' helper function does what its name implies by running: git show-index <"$1" | cut -d' ' -f2 The test in question invokes this function like this: list_packed_objects <packa-$packasha1.idx >packa.objects && list_packed_objects <packb-$packbsha1.idx >packb.objects && test_cmp packa.objects packb.objects Note how these two callsites don't specify the name of the pack index file as the function's parameter, but redirect the function's standard input from it. This triggers an error message from the shell, as it has no filename to redirect from in the function, but this error is ignored, because it happens upstream of a pipe. Consequently, both invocations produce empty 'pack{a,b}.objects' files, and the subsequent 'test_cmp' happily finds those two empty files identical. Fix these two 'list_packed_objects' invocations by specifying the pack index files as parameters. Furthermore, eliminate the pipe in that function by replacing it with an &&-chained pair of commands using an intermediate file, so a failure of 'git show-index' or the shell redirection will fail the test. Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>