Add Context.halt() function to make halting a rule simple

lib/context.js

@@ -5,6 +5,10 @@ module.exports = class Context {
     this.payload = event.payload;
   }
 
+  halt() {
+    return Promise.reject(new Error('halted'));
+  }
+
   toRepo(object) {
     const repo = this.payload.repository;
 

lib/plugins/filter.js

@@ -1,13 +1,9 @@
 const Plugin = require('../plugin');
 
-function halt() {
-  return Promise.reject(new Error('halted'));
-}
-
 module.exports = class Filter extends Plugin {
   filter(context, fn) {
     const result = fn(context.event, context);
-    return result === false ? halt() : result;
+    return result === false ? context.halt() : result;
   }
 
   then(context, fn) {
@@ -21,6 +17,6 @@ module.exports = class Filter extends Plugin {
       return name === event.event && (!action || action === event.payload.action);
     });
 
-    return res ? Promise.resolve(res) : halt();
+    return res ? Promise.resolve(res) : context.halt();
   }
 };

test/plugins/filter.js

@@ -5,7 +5,10 @@ const createSpy = expect.createSpy;
 
 describe('filter plugin', () => {
   const event = {};
-  const context = {event};
+  const context = {
+    event,
+    halt: createSpy().andReturn(Promise.reject(new Error('halted')))
+  };
 
   let filter;