diff --git a/HISTORY.md b/HISTORY.md
index b2c7f3f..49b01da 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,3 +1,10 @@
+# 0.3 / 2022-10-15
+
+* Added the `--redis` command line argument.
+* Added Docker support.
+* Use Redis on Heroku by default to avoid flakiness caused by Heroku's dynos.
+* Change default branch name to `main`
+* Do not mail when the diff is empty.
 # v0.2.1 / 2021-09-02
 
 * Add ~= comparator and translate it to ~>. Resolves #66 (@bartkamphorst)
\ No newline at end of file
diff --git a/Rakefile b/Rakefile
index 0b13fa8..460ef6a 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,5 +1,6 @@
 require 'rubygems'
 require 'date'
+require 'tempfile'
 require 'rspec/core/rake_task'
 
 task :default => :rspec
@@ -94,15 +95,15 @@ end
 
 desc 'Create a release build and push to rubygems'
 task :release => :build do
-  unless `git branch` =~ /^\* master$/
-    puts "You must be on the master branch to release!"
+  unless `git branch` =~ /^\* main$/
+    puts "You must be on the main branch to release!"
     exit!
   end
   Rake::Task[:changelog].execute
   sh "git commit --allow-empty -a -m 'Release #{version}'"
-  sh "git pull --rebase origin master"
+  sh "git pull --rebase origin main"
   sh "git tag v#{version}"
-  sh "git push origin master"
+  sh "git push origin main"
   sh "git push origin v#{version}"
   sh "gem push pkg/#{name}-#{version}.gem"
 end
diff --git a/cutting_edge.gemspec b/cutting_edge.gemspec
index 21eaf67..41808bb 100644
--- a/cutting_edge.gemspec
+++ b/cutting_edge.gemspec
@@ -5,8 +5,8 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 2.4'
 
   s.name              = 'cutting_edge'
-  s.version           = '0.2.1'
-  s.date              = '2021-09-02'
+  s.version           = '0.3'
+  s.date              = '2022-10-15'
   s.license           = 'GPL-3.0-only'
 
   s.summary     = 'Self-hosted dependency monitoring, including shiny badges.'
@@ -33,8 +33,10 @@ Gem::Specification.new do |s|
   
   # = MANIFEST =
   s.files = %w[
+    Dockerfile
     Gemfile
-    Gemfile.lock
+    HISTORY.md
+    LATEST_CHANGES.md
     LICENSE
     Procfile
     README.md
@@ -42,6 +44,8 @@ Gem::Specification.new do |s|
     bin/cutting_edge
     config.rb
     cutting_edge.gemspec
+    docker-compose.yml
+    docker-run.sh
     heroku.config.rb
     lib/cutting_edge.rb
     lib/cutting_edge/app.rb
diff --git a/docker-compose.yml b/docker-compose.yml
index 43655ce..62b49ff 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -8,7 +8,7 @@ services:
     ports:
       - '6379:6379'
   cuttingedge:
-    image: dometto/cuttingedge:master
+    image: dometto/cuttingedge:main
     environment:
       REDIS_HOST: cache
     command:
diff --git a/heroku.config.rb b/heroku.config.rb
index ebec097..daab7b6 100644
--- a/heroku.config.rb
+++ b/heroku.config.rb
@@ -16,7 +16,7 @@ module CuttingEdge
   end
   # Your additional configuration goes here.
   # If you are going to host the repository containing this file publically (e.g. on GitHub), please read:
-  # https://github.com/repotag/cutting_edge/blob/master/README.md#Defining-repositories-in-configrb
+  # https://github.com/repotag/cutting_edge/blob/main/README.md#Defining-repositories-in-configrb
 end
 
 # Needed to write to Heroku logs.
diff --git a/lib/cutting_edge.rb b/lib/cutting_edge.rb
index 0839050..251a75b 100644
--- a/lib/cutting_edge.rb
+++ b/lib/cutting_edge.rb
@@ -1,3 +1,3 @@
 module CuttingEdge
-  VERSION = '0.2.1'
+  VERSION = '0.3'
 end