Indent multiline failure messages in the output of withContext

This makes it easier to see where each failure message begins and ends.

Before:
   Some context: a
   multiline
   message

After:
   Some context:
       a
       multiline
       message

lib/jasmine-core/jasmine.js

@@ -3495,9 +3495,19 @@ getJasmineRequireObj().Expectation = function(j$) {
   }
 
   ContextAddingFilter.prototype.modifyFailureMessage = function(msg) {
-    return this.message + ': ' + msg;
+    var nl = msg.indexOf('\n');
+
+    if (nl === -1) {
+      return this.message + ': ' + msg;
+    } else {
+      return this.message + ':\n' + indent(msg);
+    }
   };
 
+  function indent(s) {
+    return s.replace(/^/gm, '    ');
+  }
+
   return {
     factory: function(options) {
       return new Expectation(options || {});

spec/core/ExpectationSpec.js

@@ -589,6 +589,32 @@ describe('Expectation', function() {
       );
     });
 
+    it('indents a multiline failure message', function() {
+      var matchers = {
+          toFoo: function() {
+            return {
+              compare: function() {
+                return { pass: false, message: 'a\nmultiline\nmessage' };
+              }
+            };
+          }
+        },
+        addExpectationResult = jasmine.createSpy('addExpectationResult'),
+        expectation = jasmineUnderTest.Expectation.factory({
+          customMatchers: matchers,
+          actual: 'an actual',
+          addExpectationResult: addExpectationResult
+        }),
+        actualMessage;
+
+      expectation.withContext('Some context').toFoo('hello');
+
+      actualMessage = addExpectationResult.calls.argsFor(0)[1].message;
+      expect(actualMessage).toEqual(
+        'Some context:\n    a\n    multiline\n    message'
+      );
+    });
+
     it('prepends the context to a custom failure message from a function', function() {
       var matchers = {
           toFoo: function() {

src/core/Expectation.js

@@ -176,9 +176,19 @@ getJasmineRequireObj().Expectation = function(j$) {
   }
 
   ContextAddingFilter.prototype.modifyFailureMessage = function(msg) {
-    return this.message + ': ' + msg;
+    var nl = msg.indexOf('\n');
+
+    if (nl === -1) {
+      return this.message + ': ' + msg;
+    } else {
+      return this.message + ':\n' + indent(msg);
+    }
   };
 
+  function indent(s) {
+    return s.replace(/^/gm, '    ');
+  }
+
   return {
     factory: function(options) {
       return new Expectation(options || {});