fast-import: zero all of 'struct tag' to silence valgrind
When running t9300, valgrind (correctly) complains about an uninitialized value in write_crash_report:
==2971== Use of uninitialised value of size 8 ==2971== at 0x4164F4: sha1_to_hex (hex.c:70) ==2971== by 0x4073E4: die_nicely (fast-import.c:468) ==2971== by 0x43284C: die (usage.c:86) ==2971== by 0x40420D: main (fast-import.c:2731) ==2971== Uninitialised value was created by a heap allocation ==2971== at 0x4C29B3D: malloc (vg_replace_malloc.c:263) ==2971== by 0x433645: xmalloc (wrapper.c:35) ==2971== by 0x405DF5: pool_alloc (fast-import.c:619) ==2971== by 0x407755: pool_calloc.constprop.14 (fast-import.c:634) ==2971== by 0x403F33: main (fast-import.c:3324)
Fix this by zeroing all of the 'struct tag'. We would only need to zero out the 'sha1' field, but this way seems more future-proof.
Signed-off-by: Thomas Rast <email@example.com> Signed-off-by: Junio C Hamano <firstname.lastname@example.org>