From 6c651604f47d9d7bcb32dd5ffa4f863d9d70df8c Mon Sep 17 00:00:00 2001
From: Guillaume Maudoux <layus.on@gmail.com>
Date: Wed, 29 Jan 2020 15:15:04 +0100
Subject: [PATCH 1/2] sane module: support overriding config files

---
 pkgs/applications/graphics/sane/config.nix | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/pkgs/applications/graphics/sane/config.nix b/pkgs/applications/graphics/sane/config.nix
index c0a0206ddd1..e134391f58c 100644
--- a/pkgs/applications/graphics/sane/config.nix
+++ b/pkgs/applications/graphics/sane/config.nix
@@ -6,7 +6,7 @@ with stdenv.lib;
 let installSanePath = path: ''
       if [ -e "${path}/lib/sane" ]; then
         find "${path}/lib/sane" -maxdepth 1 -not -type d | while read backend; do
-          ln -s "$backend" "$out/lib/sane/$(basename "$backend")"
+          symlink "$backend" "$out/lib/sane/$(basename "$backend")"
         done
       fi
 
@@ -16,14 +16,14 @@ let installSanePath = path: ''
           if [ "$name" = "dll.conf" ] || [ "$name" = "saned.conf" ] || [ "$name" = "net.conf" ]; then
             cat "$conf" >> "$out/etc/sane.d/$name"
           else
-            ln -s "$conf" "$out/etc/sane.d/$name"
+            symlink "$conf" "$out/etc/sane.d/$name"
           fi
         done
       fi
 
       if [ -e "${path}/etc/sane.d/dll.d" ]; then
         find "${path}/etc/sane.d/dll.d" -maxdepth 1 -not -type d | while read conf; do
-          ln -s "$conf" "$out/etc/sane.d/dll.d/$(basename $conf)"
+          symlink "$conf" "$out/etc/sane.d/dll.d/$(basename $conf)"
         done
       fi
     '';
@@ -33,6 +33,14 @@ stdenv.mkDerivation {
   phases = "installPhase";
 
   installPhase = ''
+    function symlink () {
+      local target=$1 linkname=$2
+      if [ -e "$linkname" ]; then
+        echo "warning: conflict for $linkname. Overriding."
+      fi
+      ln -sfn "$target" "$linkname"
+    }
+
     mkdir -p $out/etc/sane.d $out/etc/sane.d/dll.d $out/lib/sane
   '' + concatMapStrings installSanePath paths;
 }

From 4979541cadc8977c5e98b28ce245be5720422eb5 Mon Sep 17 00:00:00 2001
From: Guillaume Maudoux <layus.on@gmail.com>
Date: Mon, 10 Feb 2020 17:28:37 +0100
Subject: [PATCH 2/2] sane module: make warning more explicit

---
 pkgs/applications/graphics/sane/config.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkgs/applications/graphics/sane/config.nix b/pkgs/applications/graphics/sane/config.nix
index e134391f58c..2ef1e26f5ac 100644
--- a/pkgs/applications/graphics/sane/config.nix
+++ b/pkgs/applications/graphics/sane/config.nix
@@ -36,7 +36,7 @@ stdenv.mkDerivation {
     function symlink () {
       local target=$1 linkname=$2
       if [ -e "$linkname" ]; then
-        echo "warning: conflict for $linkname. Overriding."
+        echo "warning: conflict for $linkname. Overriding $(readlink $linkname) with $target."
       fi
       ln -sfn "$target" "$linkname"
     }