Fix inputs with empty string (#9)

* check presence
* check input type

Author: MiguelSavignano

lib/index.rb

@@ -2,13 +2,18 @@
 require 'octokit'
 require_relative './services/merge_branch_service'
 
+def presence(value)
+  return nil if value == ""
+  value
+end
+
 @event = JSON.parse(File.read(ENV['GITHUB_EVENT_PATH']))
-@head_to_merge = ENV['INPUT_HEAD_TO_MERGE'] || ENV['INPUT_FROM_BRANCH'] || ENV['GITHUB_SHA'] # or brach name
+@head_to_merge = presence(ENV['INPUT_HEAD_TO_MERGE']) || presence(ENV['INPUT_FROM_BRANCH']) || presence(ENV['GITHUB_SHA']) # or brach name
 @repository = ENV['GITHUB_REPOSITORY']
-@github_token = ENV['INPUT_GITHUB_TOKEN'] || ENV['GITHUB_TOKEN']
+@github_token = presence(ENV['INPUT_GITHUB_TOKEN']) || presence(ENV['GITHUB_TOKEN'])
 
 inputs = {
-  type: ENV['INPUT_TYPE'] || MergeBrachService::TYPE_LABELED, # labeled | comment | now
+  type: presence(ENV['INPUT_TYPE']) || MergeBrachService::TYPE_LABELED, # labeled | comment | now
   label_name: ENV['INPUT_LABEL_NAME'],
   target_branch: ENV['INPUT_TARGET_BRANCH']
 }