code: function(gitStashLocation, indexMessage, workingDirectoryMessage, includeUntracked){
  			var service = this;
  			
  			var payload = {};
  			if(indexMessage != null) /* note that undefined == null */
  				payload.IndexMessage = indexMessage;
  			
  			if(workingDirectoryMessage != null) /* note that undefined == null */
  				payload.WorkingDirectoryMessage = workingDirectoryMessage;
  			
  			if(includeUntracked === true)
  				payload.IncludeUntracked = true;
  			
  			var clientDeferred = new Deferred();
  			xhr("POST", gitStashLocation, {
  				headers : { 
  					"Orion-Version" : "1",
  					"Content-Type" : contentType
  				},
  				timeout : GIT_TIMEOUT,
  				data: JSON.stringify(payload)
  			}).then(function(result) {
  				service._getGitServiceResponse(clientDeferred, result);
  			}, function(error){
  				service._handleGitServiceResponseError(clientDeferred, error);
  			});
  			
  			return clientDeferred;
  		}
docs: Performs git stash create
  @param gitStashLocation
  @param indexMessage [optional)
  @param workingDirectoryMessage [optional]
  @param includeUntracked [optional]
  @returns {Deferred}