t1400: switch hard-coded object ID to variable

Switch a hard-coded all-zeros object ID to use a variable instead.

Signed-off-by: brian m. carlson <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: bk2204

t/t1400-update-ref.sh

@@ -346,7 +346,7 @@ test_expect_success "verifying $m's log (logged by config)" '
 
 git update-ref $m $D
 cat >.git/logs/$m <<EOF
-0000000000000000000000000000000000000000 $C $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150320 -0500
+$Z $C $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150320 -0500
 $C $A $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150350 -0500
 $A $B $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150380 -0500
 $F $Z $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150680 -0500