Expose clearUpdates method to RN for purging downloaded packages (#1269)

This is useful when changing to a deployment with an older version than
the currently installed package.

CodePush.js

@@ -542,6 +542,7 @@ if (NativeCodePush) {
     sync,
     disallowRestart: RestartManager.disallow,
     allowRestart: RestartManager.allow,
+    clearUpdates: NativeCodePush.clearUpdates,
     InstallMode: {
       IMMEDIATE: NativeCodePush.codePushInstallModeImmediate, // Restart the app immediately
       ON_NEXT_RESTART: NativeCodePush.codePushInstallModeOnNextRestart, // Don't artificially restart the app. Allow the update to be "picked up" on the next app restart

android/app/src/main/java/com/microsoft/codepush/react/CodePushNativeModule.java

@@ -587,4 +587,9 @@ public class CodePushNativeModule extends ReactContextBaseJavaModule {
             CodePushUtils.log(e);
         }
     }
+
+    @ReactMethod
+    public void clearUpdates() {
+        mCodePush.clearUpdates();
+    }
 }

docs/api-js.md

@@ -28,6 +28,8 @@ When you require `react-native-code-push`, the module object provides the follow
 
 * [sync](#codepushsync): Allows checking for an update, downloading it and installing it, all with a single call. Unless you need custom UI and/or behavior, we recommend most developers to use this method when integrating CodePush into their apps
 
+* [clearUpdates](#clearupdates): Clear all downloaded CodePush updates. This is useful when switching to a different deployment which may have an older release than the current package.
+
 #### codePush
 
 ```javascript

ios/CodePush/CodePush.m

@@ -209,8 +209,6 @@ static NSString *bundleResourceSubdirectory = nil;
     [CodePushConfig current].deploymentKey = deploymentKey;
 }
 
-#pragma mark - Test-only methods
-
 /*
  * WARNING: This cleans up all downloaded and pending updates.
  */
@@ -221,6 +219,8 @@ static NSString *bundleResourceSubdirectory = nil;
     [self removeFailedUpdates];
 }
 
+#pragma mark - Test-only methods
+
 /*
  * This returns a boolean value indicating whether CodePush has
  * been set to run under a test configuration.
@@ -867,6 +867,14 @@ RCT_EXPORT_METHOD(restartApp:(BOOL)onlyIfUpdateIsPending
     resolve(@(NO));
 }
 
+/*
+ * This method clears CodePush's downloaded updates.
+ * It is needed to switch to a different deployment if the current deployment is more recent.
+ */
+RCT_EXPORT_METHOD(clearUpdates) {
+    [CodePush clearUpdates];
+}
+
 #pragma mark - JavaScript-exported module methods (Private)
 
 /*

typings/react-native-code-push.d.ts

@@ -273,6 +273,12 @@ declare namespace CodePush {
      */
     function disallowRestart(): void;
 
+    /**
+     * Clear all downloaded CodePush updates.
+     * This is useful when switching to a different deployment which may have an older release than the current package.
+     */
+    function clearUpdates(): void;
+
     /**
      * Immediately restarts the app.
      *