Merge branch 'dev/no_replace' of https://github.com/raphink/github-changelog-generator into raphink-dev/no_replace

README.md

@@ -104,6 +104,14 @@ So, if you got error like this:
 
 It's time to create this token or wait for 1 hour before GitHub reset the counter for your IP.
 
+## Migrating from a manual changelog
+
+Knowing how dedicated you are to your project, you probably haven't been waiting for github-changelog-generator to keep a changelog,
+but you most likely wouln't like to have to open issues and PRs for all past features listed in your historic changelog.
+
+That's where `--base` comes handy. This option lets you pass a static changelog to be appended at the end of the generated entries.
+
+If you have a `HISTORY.md` file in your project, it will automatically be picked as the static historical changelog and appended.
 
 ### Rake task
 

lib/github_changelog_generator/generator/generator_generation.rb

@@ -16,6 +16,8 @@ module GitHubChangelogGenerator
         log += generate_log_for_all_tags
       end
 
+      log += File.read(@options[:base]) if File.file?(@options[:base])
+
       log += "\n\n\\* *This Change Log was automatically generated by [github_changelog_generator](https://github.com/skywinder/Github-Changelog-Generator)*"
       @log = log
     end

lib/github_changelog_generator/generator/generator_tags.rb

@@ -52,6 +52,14 @@ module GitHubChangelogGenerator
       [newer_tag_link, newer_tag_name, newer_tag_time]
     end
 
+    def detect_since_tag
+      if @options[:base] && File.file?(@options[:base])
+        reader = GitHubChangelogGenerator::Reader.new
+        content = reader.read(@options[:base])
+        return content[0]["version"] if content
+      end
+    end
+
     # Return tags after filtering tags in lists provided by option: --between-tags & --exclude-tags
     #
     # @return [Array]
@@ -64,6 +72,7 @@ module GitHubChangelogGenerator
     def filter_since_tag(all_tags)
       filtered_tags = all_tags
       tag = @options[:since_tag]
+      tag ||= detect_since_tag
       if tag
         if all_tags.map(&:name).include? tag
           idx = all_tags.index { |t| t.name == tag }

lib/github_changelog_generator/parser.rb

@@ -50,6 +50,9 @@ module GitHubChangelogGenerator
         opts.on("-o", "--output [NAME]", "Output file. Default is CHANGELOG.md") do |last|
           options[:output] = last
         end
+        opts.on("-b", "--base [NAME]", "Optional base file to append generated changes to.") do |last|
+          options[:base] = last
+        end
         opts.on("--bugs-label [LABEL]", "Setup custom label for bug-fixes section. Default is \"**Fixed bugs:**""") do |v|
           options[:bug_prefix] = v
         end
@@ -156,6 +159,7 @@ module GitHubChangelogGenerator
         tag2: nil,
         date_format: "%Y-%m-%d",
         output: "CHANGELOG.md",
+        base: "HISTORY.md",
         issues: true,
         add_issues_wo_labels: true,
         add_pr_wo_labels: true,