Add release-branch option to filter the Pull Requests by those applied on a partcular release branch

lib/github_changelog_generator/fetcher.rb

@@ -22,6 +22,7 @@ module GitHubChangelogGenerator
       github_options[:oauth_token] = @github_token unless @github_token.nil?
       github_options[:endpoint] = @options[:github_endpoint] unless @options[:github_endpoint].nil?
       github_options[:site] = @options[:github_endpoint] unless @options[:github_site].nil?
+      @release_branch = @options[:release_branch] unless @options[:release_branch].nil?
 
       @github = check_github_response { Github.new github_options }
     end
@@ -123,7 +124,11 @@ Make sure, that you push tags to remote repo via 'git push --tags'".yellow
     def fetch_closed_pull_requests
       pull_requests = []
       begin
-        response = @github.pull_requests.list @options[:user], @options[:project], state: "closed"
+        if @options[:release_branch].nil?
+          response = @github.pull_requests.list @options[:user], @options[:project], state: "closed"
+        else
+          response = @github.pull_requests.list @options[:user], @options[:project], state: "closed", base: @options[:release_branch]
+        end
         page_i = 0
         count_pages = response.count_pages
         response.each_page do |page|

lib/github_changelog_generator/generator/generator_processor.rb

@@ -178,8 +178,10 @@ module GitHubChangelogGenerator
         fetched_pr = closed_pull_requests.find do |fpr|
           fpr.number == pr.number
         end
-        pr[:merged_at] = fetched_pr[:merged_at]
-        closed_pull_requests.delete(fetched_pr)
+        unless fetched_pr.nil?
+          pr[:merged_at] = fetched_pr[:merged_at]
+          closed_pull_requests.delete(fetched_pr)
+        end
       end
 
       pull_requests.select! do |pr|

lib/github_changelog_generator/parser.rb

@@ -143,6 +143,9 @@ module GitHubChangelogGenerator
         opts.on("--future-release [RELEASE-VERSION]", "Put the unreleased changes in the specified release number.") do |future_release|
           options[:future_release] = future_release
         end
+        opts.on("--release-branch [RELEASE-BRANCH]", "Limit pull requests to the release branch, such as master or release") do |release_branch|
+          options[:release_branch] = release_branch
+        end
         opts.on("--[no-]verbose", "Run verbosely. Default is true") do |v|
           options[:verbose] = v
         end

lib/github_changelog_generator/task.rb

@@ -16,7 +16,8 @@ module GitHubChangelogGenerator
                   bug_labels enhancement_labels
                   between_tags exclude_tags since_tag max_issues
                   github_site github_endpoint simple_list
-                  future_release verbose release_url base )
+                  future_release release_branch verbose release_url 
+                  base )
 
     OPTIONS.each do |o|
       attr_accessor o.to_sym