debian: adding divertion for existing bash completion file

Signed-off-by: Julien Fortin <julien@cumulusnetworks.com>

debian/ifupdown2.postrm

@@ -42,6 +42,25 @@ postrm_purge()
 	rm -f /run/network/ifstatenew
 }
 
+# restore file if we diverted it on install/upgrade
+_postrm_divert()
+{
+    diversions=$(dpkg-divert --list | grep "$1" | grep 'by ifupdown2$'  | wc -l 2> /dev/null)
+    if [ $diversions -gt 0 ] ;
+    then
+        dpkg-divert --remove --package ifupdown2 --rename $1
+    fi
+}
+
+postrm_divert()
+{
+    for filename in ifup ifdown ifquery ifreload
+    do
+        _postrm_divert "/usr/share/bash-completion/completions/$filename"
+        _postrm_divert "/etc/bash_completion.d/$filename"
+    done
+}
+
 case "$1" in
 	purge)
 		postrm_purge
@@ -49,10 +68,14 @@ case "$1" in
 
 	remove)
 		postrm_remove
+		postrm_divert
 	;;
 
+    abort-install|disappear|failed-upgrade|abort-upgrade)
+        postrm_divert
+    ;;
 
-	upgrade|disappear|failed-upgrade|abort-install|abort-upgrade)
+	upgrade)
 	;;
 
 	*)

debian/ifupdown2.preinst

@@ -1,11 +1,39 @@
 #! /bin/sh
+
+MYNAME="${0##*/}"
+
+report() { echo "${MYNAME}: $*" ; }
+report_err() { report "Error: $*" >&2 ; }
+
+preinst_divert()
+{
+    diversions=$(dpkg-divert --list | grep "$1" | grep -v 'by ifupdown2$'  | wc -l 2> /dev/null)
+    if [ $diversions -gt 0 ] ;
+    then
+        report_err "existing diversion for $1"
+    else
+        if [ -f $1 ];
+        then
+            dpkg-divert --add --package ifupdown2 --rename --divert "$1.disabled" "$1"
+        fi
+    fi
+}
+
 set -e
 case "$1" in
     install|upgrade)
+        for filename in ifup ifdown ifquery ifreload
+        do
+            preinst_divert "/usr/share/bash-completion/completions/$filename"
+            preinst_divert "/etc/bash_completion.d/$filename"
+        done
+
+        # workaround 3.0.0 internal install error.  This can be removed in a
+        # few weeks.
         if [ -f /etc/default/networking/networking.default ]; then
-	    dpkg-maintscript-helper rm_conffile /etc/default/networking/networking.default 1.1 -- $@
-	    rm -f /etc/default/networking/networking.default
-	    rmdir /etc/default/networking
+            dpkg-maintscript-helper rm_conffile /etc/default/networking/networking.default 1.1 -- $@
+            rm -f /etc/default/networking/networking.default
+            rmdir /etc/default/networking
         fi
         ;;
 esac