add preference to disable removable storage scanning

app/src/full/java/org/fdroid/fdroid/localrepo/SDCardScannerService.java

@@ -30,8 +30,9 @@ import android.os.Environment;
 import android.os.Process;
 import android.support.v4.content.ContextCompat;
 import android.util.Log;
-import org.fdroid.fdroid.IndexV1Updater;
 import org.fdroid.fdroid.IndexUpdater;
+import org.fdroid.fdroid.IndexV1Updater;
+import org.fdroid.fdroid.Preferences;
 import org.fdroid.fdroid.Utils;
 
 import java.io.File;
@@ -52,6 +53,11 @@ import java.util.List;
  * only ever allow for reading repos, never writing.  It also will not work
  * for removeable storage devices plugged in via USB, since do not show up as
  * "External Storage"
+ * <p>
+ * Scanning the removable storage requires that the user allowed it.  This
+ * requires both the {@link Preferences#isScanRemovableStorageEnabled()}
+ * and the {@link android.Manifest.permission#READ_EXTERNAL_STORAGE}
+ * permission to be enabled.
  *
  * @see TreeUriScannerIntentService TreeUri method for writing repos to be shared
  * @see <a href="https://stackoverflow.com/a/40201333">Universal way to write to external SD card on Android</a>
@@ -69,10 +75,12 @@ public class SDCardScannerService extends IntentService {
     }
 
     public static void scan(Context context) {
+        if (Preferences.get().isScanRemovableStorageEnabled()) {
             Intent intent = new Intent(context, SDCardScannerService.class);
             intent.setAction(ACTION_SCAN);
             context.startService(intent);
         }
+    }
 
     @Override
     protected void onHandleIntent(Intent intent) {

app/src/full/java/org/fdroid/fdroid/localrepo/TreeUriScannerIntentService.java

@@ -29,8 +29,9 @@ import android.support.v4.provider.DocumentFile;
 import android.util.Log;
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.IOUtils;
-import org.fdroid.fdroid.IndexV1Updater;
 import org.fdroid.fdroid.IndexUpdater;
+import org.fdroid.fdroid.IndexV1Updater;
+import org.fdroid.fdroid.Preferences;
 import org.fdroid.fdroid.Utils;
 import org.fdroid.fdroid.data.Repo;
 import org.fdroid.fdroid.data.RepoProvider;
@@ -72,11 +73,13 @@ public class TreeUriScannerIntentService extends IntentService {
     }
 
     public static void scan(Context context, Uri data) {
+        if (Preferences.get().isScanRemovableStorageEnabled()) {
             Intent intent = new Intent(context, TreeUriScannerIntentService.class);
             intent.setAction(ACTION_SCAN_TREE_URI);
             intent.setData(data);
             context.startService(intent);
         }
+    }
 
     @Override
     protected void onHandleIntent(Intent intent) {

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

@@ -92,6 +92,7 @@ public final class Preferences implements SharedPreferences.OnSharedPreferenceCh
     public static final String PREF_PRIVILEGED_INSTALLER = "privilegedInstaller";
     public static final String PREF_LOCAL_REPO_NAME = "localRepoName";
     public static final String PREF_LOCAL_REPO_HTTPS = "localRepoHttps";
+    public static final String PREF_SCAN_REMOVABLE_STORAGE = "scanRemovableStorage";
     public static final String PREF_LANGUAGE = "language";
     public static final String PREF_USE_TOR = "useTor";
     public static final String PREF_ENABLE_PROXY = "enableProxy";
@@ -400,6 +401,10 @@ public final class Preferences implements SharedPreferences.OnSharedPreferenceCh
         return preferences.getString(PREF_LOCAL_REPO_NAME, getDefaultLocalRepoName());
     }
 
+    public boolean isScanRemovableStorageEnabled() {
+        return preferences.getBoolean(PREF_SCAN_REMOVABLE_STORAGE, true);
+    }
+
     public boolean isUpdateNotificationEnabled() {
         return preferences.getBoolean(PREF_UPDATE_NOTIFICATION_ENABLED, true);
     }

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

@@ -59,6 +59,10 @@
     <string name="local_repo_name">Name of your Local Repo</string>
     <string name="local_repo_name_summary">The advertised title of your local repo: %s</string>
     <string name="local_repo_https_on">Use encrypted HTTPS:// connection for local repo</string>
+    <string name="scan_removable_storage_title">Scan removable storage</string>
+    <string name="scan_removable_storage_summary">Look for package repos on removable storage like SD Cards
+        and USB thumb drives
+    </string>
 
     <string name="login_title">Authentication required</string>
     <string name="login_name">Username</string>

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

@@ -96,6 +96,11 @@
         <EditTextPreference
                 android:key="localRepoName"
                 android:title="@string/local_repo_name"/>
+        <SwitchPreference
+                android:key="scanRemovableStorage"
+                android:defaultValue="true"
+                android:title="@string/scan_removable_storage_title"
+                android:summary="@string/scan_removable_storage_summary"/>
     </android.support.v7.preference.PreferenceCategory>
 
     <android.support.v7.preference.PreferenceCategory android:title="@string/proxy">