test-lib-functions: suppress a 'git rev-parse' error in 'test_commit_bulk'

When 'test_commit_bulk' is invoked in an empty test repository, it
prints a "fatal: Needed a single revision" error, but still does what
it's supposed to do.  A test helper function displaying a fatal error
and still succeeding is always suspect to be buggy, but luckily that's
not the case here: that error comes from a 'git rev-parse --verify
HEAD' command invoked in a condition, which doesn't have anything to
verify in an empty repository.

Use the '--quiet' option to suppress that error message.

Signed-off-by: SZEDER Gábor <[email protected]>
Acked-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: szeder

t/test-lib-functions.sh

@@ -306,7 +306,7 @@ test_commit_bulk () {
 	total=$1
 
 	add_from=
-	if git -C "$indir" rev-parse --verify "$ref"
+	if git -C "$indir" rev-parse --quiet --verify "$ref"
 	then
 		add_from=t
 	fi