rules_generator: remove policy from write_cd_rules

The decision about when to create by-id or by-path persistent rules should
be made in the generator rules file where it's obvious and easy to modify
locally, not in the script.

extras/rule_generator/75-cd-aliases-generator.rules

@@ -1,3 +1,6 @@
 # these rules generate rules for the /dev/{cdrom,dvd,...} symlinks
 
+# the path of removable devices changes frequently
+ACTION=="add", SUBSYSTEM=="block", SUBSYSTEMS=="usb|ieee1394", ENV{ID_CDROM}=="?*", ENV{GENERATED}!="?*", PROGRAM="write_cd_rules by-id", SYMLINK+="%c"
+
 ACTION=="add", SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{GENERATED}!="?*", PROGRAM="write_cd_rules", SYMLINK+="%c"

extras/rule_generator/write_cd_rules

@@ -53,15 +53,7 @@ fi
 if [ "$1" ]; then
 	METHOD="$1"
 else
-	case "$ID_BUS" in
-		usb|ieee1394)
-		METHOD='by-id'
-		;;
-
-		*)
-		METHOD='by-path'
-		;;
-	esac
+	METHOD='by-path'
 fi
 
 case "$METHOD" in