Feature: #deploy to main or master refs

README.md

@@ -61,7 +61,7 @@ Push your local development database backup up to staging:
 
     staging restore development
 
-Deploy master to production (note that prior versions of Parity would run
+Deploy main to production (note that prior versions of Parity would run
 database migrations, that's now better handled using [Heroku release phase]):
 
     production deploy

lib/parity/environment.rb

@@ -41,14 +41,27 @@ def backup
 
     def deploy
       if production?
-        Kernel.system("git push production master")
+        Kernel.system("git push production #{branch_ref}")
       else
         Kernel.system(
-          "git push #{environment} HEAD:master --force",
+          "git push #{environment} HEAD:#{branch_ref} --force",
         )
       end
     end
 
+    def branch_ref
+      main_ref_exists = system("git show-ref --verify --quiet refs/heads/main")
+      master_ref_exists = system(
+        "git show-ref --verify --quiet refs/heads/master",
+      )
+
+      if main_ref_exists && !master_ref_exists
+        "main"
+      else
+        "master"
+      end
+    end
+
     def restore
       if production? && !forced?
         $stdout.puts "Parity does not support restoring backups into your "\

spec/parity/environment_spec.rb

@@ -10,8 +10,10 @@
     backup = stub_parity_backup
     allow(Parity::Backup).to receive(:new).and_return(backup)
 
-    Parity::Environment.new("development",
-                            ["restore", "staging", "--parallelize"]).run
+    Parity::Environment.new(
+      "development",
+      ["restore", "staging", "--parallelize"],
+    ).run
 
     expect(Parity::Backup).to have_received(:new).
       with(
@@ -238,7 +240,7 @@
       once
   end
 
-  it "returns true if the deploy was succesful but no migrations needed to be run" do
+  it "returns true if deploy was successful without migrations" do
     result = Parity::Environment.new("production", ["deploy"]).run
 
     expect(result).to eq(true)
@@ -258,6 +260,26 @@
     expect(Kernel).to have_received(:system).with(git_push_feature_branch)
   end
 
+  it "deploys feature branches to staging's main for evaluation" do
+    env = Parity::Environment.new("staging", ["deploy"])
+
+    allow(env).to receive(:branch_ref).and_return("main")
+
+    env.run
+
+    expect(Kernel).to have_received(:system).with(git_push_feature_branch_main)
+  end
+
+  it "deploys main production's main for evaluation" do
+    env = Parity::Environment.new("production", ["deploy"])
+
+    allow(env).to receive(:branch_ref).and_return("main")
+
+    env.run
+
+    expect(Kernel).to have_received(:system).with(git_push_main)
+  end
+
   def heroku_backup
     "heroku pg:backups:capture --remote production"
   end
@@ -274,10 +296,18 @@ def git_push
     "git push production master"
   end
 
+  def git_push_main
+    "git push production main"
+  end
+
   def git_push_feature_branch
     "git push staging HEAD:master --force"
   end
 
+  def git_push_feature_branch_main
+    "git push staging HEAD:main --force"
+  end
+
   def migrate
       %{
         heroku run rake db:migrate --remote production &&