add Expert Pref to enable Push Requests

Since !705 will allow OEMs, ROM makers, etc. to add repos, there needs to
be a way for the user to prevent those from automatically installing or
uninstalling apps for users of the full F-Droid app, which guarantees user
control.

app/src/main/java/org/fdroid/fdroid/Preferences.java

@@ -108,6 +108,7 @@ public final class Preferences implements SharedPreferences.OnSharedPreferenceCh
     public static final String PREF_HIDE_ON_LONG_PRESS_SEARCH = "hideOnLongPressSearch";
     public static final String PREF_HIDE_ALL_NOTIFICATIONS = "hideAllNotifications";
     public static final String PREF_SEND_VERSION_AND_UUID_TO_SERVERS = "sendVersionAndUUIDToServers";
+    public static final String PREF_ALLOW_PUSH_REQUESTS = "allowPushRequests";
 
     public static final int OVER_NETWORK_NEVER = 0;
     public static final int OVER_NETWORK_ON_DEMAND = 1;
@@ -512,6 +513,16 @@ public final class Preferences implements SharedPreferences.OnSharedPreferenceCh
         return preferences.getBoolean(PREF_SEND_VERSION_AND_UUID_TO_SERVERS, IGNORED_B);
     }
 
+    /**
+     * Whether push requests are globally enabled or disabled.
+     *
+     * @see org.fdroid.fdroid.data.RepoPushRequest
+     * @see RepoUpdater#processRepoPushRequests(List)
+     */
+    public boolean allowPushRequests() {
+        return preferences.getBoolean(PREF_ALLOW_PUSH_REQUESTS, IGNORED_B);
+    }
+
     /**
      * This is cached as it is called several times inside app list adapters.
      * Providing it here means the shared preferences file only needs to be

app/src/main/java/org/fdroid/fdroid/RepoUpdater.java

@@ -442,9 +442,14 @@ public class RepoUpdater {
      * Server index XML can include optional {@code install} and {@code uninstall}
      * requests.  This processes those requests, figuring out whether the client
      * should always accept, prompt the user, or ignore those requests on a
-     * per repo basis.
+     * per repo basis.  There is also a global preference as a failsafe.
+     *
+     * @see Preferences#allowPushRequests()
      */
     void processRepoPushRequests(List<RepoPushRequest> requestEntries) {
+        if (!Preferences.get().allowPushRequests()) {
+            return;
+        }
         for (RepoPushRequest repoPushRequest : requestEntries) {
             String packageName = repoPushRequest.packageName;
             PackageInfo packageInfo = Utils.getPackageInfo(context, packageName);

app/src/main/res/values/strings.xml

@@ -33,6 +33,9 @@
         downloading, takes affect next app restart.</string>
     <string name="force_old_index">Force old index format</string>
     <string name="force_old_index_summary">In case there are bugs or compatibility issues, use the XML app index</string>
+    <string name="allow_push_requests">Allow repos to install/uninstall apps</string>
+    <string name="allow_push_requests_summary">Repo metadata can include "push requests" to install or uninstall apps
+    </string>
     <string name="other">Other</string>
 
     <string name="update_interval">Automatic update interval</string>

app/src/main/res/xml/preferences.xml

@@ -190,6 +190,12 @@
                 android:summary="@string/send_version_and_uuid_summary"
                 android:defaultValue="false"
                 android:dependency="expert"/>
+        <CheckBoxPreference
+                android:key="allowPushRequests"
+                android:title="@string/allow_push_requests"
+                android:summary="@string/allow_push_requests_summary"
+                android:defaultValue="false"
+                android:dependency="expert"/>
         <CheckBoxPreference
                 android:key="forceOldIndex"
                 android:title="@string/force_old_index"