[Breakage] Git v2.21.0-rc0 - t5318 (NonStop)

Hi All,

t5318 is rather problematic and I have no good way to fix this. There is no /dev/zero on the platform, and the corrupt_graph_and_verify hard-codes if=/dev/zero, which is a linux-specific pseudo device. Please provide a more platform independent way of testing this feature. Pretty much all subtests from 46 onward fail as a result.

expecting success:
        corrupt_graph_and_verify 0 "\0" \
                "graph signature"

1+0 records in 1+0 records out 1 byte copied, 0.002248 s, 0.4 kB/s 0+0 records in 0+0 records out 0 bytes copied, 0.001815 s, 0.0 kB/s dd: failed to open '/dev/zero': No such file or directory not ok 46 - detect bad signature # # corrupt_graph_and_verify 0 "\0" \ # "graph signature" #

Regards, Randall