infer root branch globally (#93)

lib/baes/actions/build_tree.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-SKIP_BRANCHES = ["staging", "main", "master"].freeze
-
 # class that generates a tree of dependent branches
 class Baes::Actions::BuildTree
   class << self
@@ -43,7 +41,7 @@ def prune(branch)
     end
 
     def link_branch_to_parent(branch, indexed_branches, root_branch:)
-      return if branch == root_branch || SKIP_BRANCHES.include?(branch.name)
+      return if branch == root_branch
 
       parent_branch = indexed_branches.fetch(parent_name(branch), root_branch)
 

lib/baes/branch_collection.rb

@@ -12,11 +12,7 @@ def initialize
 
   # return the root branch
   def root
-    if root_name
-      find_by_name(root_name)
-    else
-      find_by_name("main") || find_by_name("master")
-    end
+    find_by_name(root_name)
   end
 
   # find a branch by name

lib/baes/configuration.rb

@@ -34,7 +34,15 @@ def self.output=(output)
 
   # return the configured root_name
   def self.root_name
-    @root_name
+    @root_name ||=
+      begin
+        root = (["main", "master"] & git.branch_names).first
+
+        message = "unable to infer root branch, please specify with -r"
+        raise Baes::Git::GitError, message unless root
+
+        root
+      end
   end
 
   # allow setting the root_name

spec/baes/configuration_spec.rb

@@ -1,6 +1,32 @@
 # frozen_string_literal: true
 
 RSpec.describe Baes::Configuration do
+  describe ".root_name" do
+    it "returns the root branch name when set" do
+      described_class.root_name = "moon"
+
+      expect(described_class.root_name).to eq("moon")
+    end
+
+    it "defaults to 'main' when present" do
+      FakeGit.branch_names = ["main", "master"]
+
+      expect(described_class.root_name).to eq("main")
+    end
+
+    it "defaults to 'master' when 'main' is not present" do
+      FakeGit.branch_names = ["master"]
+
+      expect(described_class.root_name).to eq("master")
+    end
+
+    it "raises a GitError when neither 'main' nor 'master' are present" do
+      FakeGit.branch_names = ["moon"]
+
+      expect { described_class.root_name }.to raise_error(Baes::Git::GitError)
+    end
+  end
+
   describe ".auto_skip?" do
     it "defaults to false" do
       expect(described_class.auto_skip?).to be(false)