debian packaging: fix removed diversion (take II; followup 8b054e6; reverts 5f310a7)

debian/control.in

@@ -84,8 +84,7 @@ Recommends:
  qgis-provider-grass,
  qgis-plugin-globe
 Suggests: gpsbabel
-Replaces: qgis-plugin-grass (<< 1:2.13.0+git20160204)
-Conflicts: uim-qt3, qgis-plugin-grass (<< 1:2.13.0+git20160204)
+Conflicts: uim-qt3
 Description: Geographic Information System (GIS)
  A Geographic Information System (GIS) manages, analyzes, and displays
  databases of geographic information. QGIS supports shape file viewing and

debian/qgis.preinst

@@ -0,0 +1,23 @@
+#!/bin/sh
+
+set -e
+
+if [ "$1" = "install" -o "$1" = "upgrade" ]; then
+	# Fix bad diversions
+        div=$(dpkg-divert --listpackage /usr/bin/qgis)
+        if [ -n "$div" -a "$div" = qgis-plugin-grass ]; then
+               for i in /usr/bin/qgis /usr/bin/qbrowser; do
+                       if [ -e $i ] && ! [ -e $i.undiverted ]; then
+                               mv $i $i.undiverted
+                       fi
+                       dpkg-divert --package qgis-plugin-grass --remove --rename --divert $i.bin $i
+                       if [ -e $i.undiverted ]; then
+                               mv $i.undiverted $i
+                       fi
+               done
+       fi
+fi
+
+#DEBHELPER#
+
+exit 0

debian/qgis.sh.in

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-if dpkg -s qgis-plugin-grass >/dev/null; then
+if dpkg -s qgis-plugin-grass >/dev/null 2>&1; then
 	if [ "$LD_LIBRARY_PATH" = "" ]; then
 		LD_LIBRARY_PATH=/usr/lib/{GRASS}/lib
 	else
@@ -8,7 +8,7 @@ if dpkg -s qgis-plugin-grass >/dev/null; then
 	fi
 fi
 
-if dpkg -s qgis-oracle-provider >/dev/null; then
+if dpkg -s qgis-oracle-provider >/dev/null 2>&1; then
 	if [ "$LD_LIBRARY_PATH" = "" ]; then
 		LD_LIBRARY_PATH={ORACLE_LIBDIR}
 	else