From 65e40c8c3452fcb9769598a693bb3c855ff277ab Mon Sep 17 00:00:00 2001
From: Johannes 'josch' Schauer <josch@mister-muffin.de>
Date: Wed, 2 Sep 2020 22:58:20 +0200
Subject: [PATCH] redirect stderr of dpkg --version to /dev/null to prevent
 error output if dpkg is too old (thanks Trent W. Buck!)

---
 mmdebstrap | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/mmdebstrap b/mmdebstrap
index ad0c0e4..8ff5253 100755
--- a/mmdebstrap
+++ b/mmdebstrap
@@ -1289,8 +1289,14 @@ sub run_setup() {
 
     my $dpkgversion;
     {
-        open my $fh, '-|', 'dpkg', '--robot',
-          '--version' // error "failed to fork(): $!";
+        my $pid = open my $fh, '-|' // error "failed to fork(): $!";
+        if ($pid == 0) {
+            # redirect stderr to /dev/null to hide error messages from dpkg
+            # versions before 1.20.0
+            open(STDERR, '>', '/dev/null')
+              or error "cannot open /dev/null for writing: $!";
+            exec 'dpkg', '--robot', '--version';
+        }
         chomp(
             $dpkgversion = do { local $/; <$fh> }
         );