Refactor __package_update_index explorers

* add an type explorer to unify detecting of package type.
* update currage use the type explorer, so if os and passed in type
does not match, it behaves correctly.

cdist/conf/type/__package_update_index/explorer/currage

@@ -17,17 +17,17 @@
 # You should have received a copy of the GNU General Public License
 # along with cdist. If not, see <http://www.gnu.org/licenses/>.
 
-os="$("$__explorer/os")"
+type="$($__type_explorer/type)"
 
-case "$os" in
-    debian|ubuntu|devuan)
+case "$type" in
+    apt)
         if [ -f "/var/cache/apt/pkgcache.bin" ]; then
             echo $(($(date +"%s")-$(stat --format '%Y' /var/cache/apt/pkgcache.bin)))
         else
             echo 0
         fi
         ;;
-    *)  echo "Your operating system ($os) is currently not supported by this type (${__type##*/})." >&2
+    *)  echo "Your specified type ($type) is currently not supported." >&2
         echo "Please contribute an implementation for it if you can." >&2
         ;;
 esac

cdist/conf/type/__package_update_index/explorer/type

@@ -0,0 +1,34 @@
+#!/bin/sh
+#
+# 2018 Stu Zhao (z12y12l12 at gmail.com)
+#
+# This file is part of cdist.
+#
+# cdist is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# cdist is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with cdist. If not, see <http://www.gnu.org/licenses/>.
+
+if [ -f "$__object/parameter/type" ]; then
+    cat "$__object/parameter/type"
+else
+    # By default determine package manager based on operating system
+    os="$($__explorer/os)"
+    case "$os" in
+        amazon|scientific|centos|fedora|redhat) echo "yum" ;;
+        debian|ubuntu|devuan) echo "apt" ;;
+        archlinux) echo "pacman" ;;
+        *)
+            echo "Don't know how to manage packages on: $os" >&2
+            exit 1
+            ;;
+    esac
+fi

cdist/conf/type/__package_update_index/gencode-remote

@@ -21,28 +21,12 @@
 # Update the package index with the appropriate package manager
 #
 
-type="$__object/parameter/type"
+type=$(cat "$__object/explorer/type")
 if [ -f "$__object/parameter/maxage" ]; then
     maxage="$(cat "$__object/parameter/maxage")"
     currage="$(cat "$__object/explorer/currage")"
 fi
 
-if [ -f "$type" ]; then
-    type="$(cat "$type")"
-else
-    # By default determine package manager based on operating system
-    os="$(cat "$__global/explorer/os")"
-    case "$os" in
-        amazon|scientific|centos|fedora|redhat) type="yum" ;;
-        debian|ubuntu|devuan) type="apt" ;;
-        archlinux) type="pacman" ;;
-        *)
-            echo "Don't know how to manage packages on: $os" >&2
-            exit 1
-            ;;
-    esac
-fi
-
 if [ -n "$maxage" ] && [ "$type" != "apt" ]; then
     echo "ERROR: \"--maxage\" only supported for \"apt\" pkg-manager." >&2
     exit 1