Add breaking-changes section to changelog (#530)

* add breaking-changes section to changelog

* Clean up parse_by_sections

* Thank you bastelfreak and ekohl!

lib/github_changelog_generator/parser.rb

@@ -70,6 +70,9 @@ module GitHubChangelogGenerator
         opts.on("--enhancement-label [LABEL]", "Setup custom label for enhancements section. Default is \"**Implemented enhancements:**\"") do |v|
           options[:enhancement_prefix] = v
         end
+        opts.on("--breaking-label [LABEL]", "Setup custom label for the breaking changes section. Default is \"**Breaking changes:**\"") do |v|
+          options[:breaking_prefix] = v
+        end
         opts.on("--issues-label [LABEL]", "Setup custom label for closed-issues section. Default is \"**Closed issues:**\"") do |v|
           options[:issue_prefix] = v
         end
@@ -127,6 +130,9 @@ module GitHubChangelogGenerator
         opts.on("--enhancement-labels  x,y,z", Array, 'Issues with the specified labels will be always added to "Implemented enhancements" section. Default is \'enhancement,Enhancement\'') do |list|
           options[:enhancement_labels] = list
         end
+        opts.on("--breaking-labels x,y,z", Array, 'Issues with these labels will be added to a new section, called "Breaking Changes". Default is \'backwards-incompatible\'') do |list|
+          options[:breaking_labels] = list
+        end
         opts.on("--issue-line-labels x,y,z", Array, 'The specified labels will be shown in brackets next to each matching issue. Use "ALL" to show all labels. Default is [].') do |list|
           options[:issue_line_labels] = list
         end
@@ -208,6 +214,7 @@ module GitHubChangelogGenerator
         enhancement_labels: ["enhancement", "Enhancement", "Type: Enhancement"],
         bug_labels: ["bug", "Bug", "Type: Bug"],
         exclude_labels: ["duplicate", "question", "invalid", "wontfix", "Duplicate", "Question", "Invalid", "Wontfix", "Meta: Exclude From Changelog"],
+        breaking_labels: %w[backwards-incompatible breaking],
         issue_line_labels: [],
         max_issues: nil,
         simple_list: false,
@@ -218,6 +225,7 @@ module GitHubChangelogGenerator
         issue_prefix: "**Closed issues:**",
         bug_prefix: "**Fixed bugs:**",
         enhancement_prefix: "**Implemented enhancements:**",
+        breaking_prefix: "**Breaking changes:**",
         http_cache: true
       )
     end