testcommon: spawn-aware system() and qx[] workalikes

Barely noticeable on Linux, but this gives a 1-2% speedup
on a FreeBSD 11.3 VM and lets us use built-in redirects
rather than relying on /bin/sh.

1 files changed, 3 insertions, 2 deletions

diff --git a/t/init.t b/t/init.t
index a78c2fc8..94c6184e 100644
--- a/t/init.t
+++ b/t/init.t
@@ -105,7 +105,8 @@ done_testing();
 
 sub read_indexlevel {
         my ($inbox) = @_;
-        local $ENV{GIT_CONFIG} = "$ENV{PI_DIR}/config";
-        chomp(my $lvl = `git config publicinbox.$inbox.indexlevel`);
+        my $cmd = [ qw(git config), "publicinbox.$inbox.indexlevel" ];
+        my $env = { GIT_CONFIG => "$ENV{PI_DIR}/config" };
+        chomp(my $lvl = xqx($cmd, $env));
         $lvl;
 }