Merge remote-tracking branch 'origin/pr/18'

* origin/pr/18:
  fixed "in place upgrade issue - base-passwd debconf interative questi…on asks 'Remove group "qubes"'" for existing users

debian/qubes-core-agent.preinst

@@ -59,7 +59,15 @@ if [ "$1" = "install" ] ; then
 fi
 
 if [ "$1" = "upgrade" ] ; then
-    true 
+    ## Fix static gid issue for in place template upgrades.
+    ## https://github.com/QubesOS/qubes-issues/issues/1105
+    if grep -q ^qubes:x:98: /etc/group ; then
+        if ! grep -q :980: /etc/group ; then
+            if groupmod -g 980 qubes ; then
+                find / -gid 98 ! -type l -exec chgrp --verbose qubes {} \; 2>/dev/null || true
+            fi
+        fi
+    fi
 fi
 
 # dh_installdeb will replace this with shell code automatically