From 76bf44393cbd4de3fac3f4535c8383c329f4e6b4 Mon Sep 17 00:00:00 2001
From: Andrew Cady <d@jerkface.net>
Date: Fri, 16 Oct 2020 13:08:28 -0400
Subject: handling of apt sources is intelligenter

---
 selfpublish.sh | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/selfpublish.sh b/selfpublish.sh
index 0d9dd96..eb3c5d9 100644
--- a/selfpublish.sh
+++ b/selfpublish.sh
@@ -37,12 +37,25 @@ apt_install()
     as_root apt-get install "$@"
 }
 
+write_line_once()
+{
+    local line="$2" target_file="$1"
+    if grep -qF "$line" "$target_file"
+    then
+        return
+    else
+        printf %s "$line" | as_root tee -a "$target_file" >/dev/null
+    fi
+}
+
 dpkg_install()
 {
     case "$(lsb_release -cs)" in
         buster)
-            echo 'deb      http://httpredir.debian.org/debian  buster-backports  main' |
-                as_root tee -a /etc/apt/sources.list.d/buster-backports.list >/dev/null ;;
+            apt-cache policy | grep -q 'http://httpredir.debian.org/debian buster-backports/main' ||
+                write_line_once /etc/apt/sources.list.d/buster-backports.list \
+                    'deb      http://httpredir.debian.org/debian  buster-backports  main'
+            ;;
     esac
 
     as_root $SHELL -c "set -$- +e; dpkg -i $*; apt-get -t buster-backports -f install"
-- 
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