Use of uninitialised value of size 8 in sha1_name.c

Hi Derrick,

These days when running:

./t5616-partial-clone.sh --valgrind

on master, I get a bunch of:

==21455== Use of uninitialised value of size 8 ==21455== at 0x2D2A73: get_hex_char_from_oid (sha1_name.c:492) ==21455== by 0x2D2AFE: extend_abbrev_len (sha1_name.c:502) ==21455== by 0x2D2C3D: find_abbrev_len_for_pack (sha1_name.c:551) ==21455== by 0x2D2CFF: find_abbrev_len_packed (sha1_name.c:569) ==21455== by 0x2D2E12: find_unique_abbrev_r (sha1_name.c:608) ==21455== by 0x2DCB66: strbuf_add_unique_abbrev (strbuf.c:877) ==21455== by 0x14F7CE: update_local_ref (fetch.c:700) ==21455== by 0x1500CF: store_updated_refs (fetch.c:871) ==21455== by 0x15035B: fetch_refs (fetch.c:932) ==21455== by 0x150CF8: do_fetch (fetch.c:1146) ==21455== by 0x1515AB: fetch_one (fetch.c:1370) ==21455== by 0x151A1D: cmd_fetch (fetch.c:1457) ==21455== Uninitialised value was created by a stack allocation ==21455== at 0x2D2B2E: find_abbrev_len_for_pack (sha1_name.c:513) ==21455==

A quick git blame seems to point to 0e87b85683 (sha1_name: minimize OID comparisons during disambiguation, 2017-10-12).

It is difficult to tell for sure though as t5616-partial-clone.sh was added after that commit.

Best, Christian.