introduce BranchCollection class (#78)

This will encapsulate more logic for finding branches

lib/baes.rb

@@ -10,5 +10,6 @@ class Baes::Error < StandardError; end
 
 require_relative "baes/actions"
 require_relative "baes/branch"
+require_relative "baes/branch_collection"
 require_relative "baes/git"
 require_relative "baes/version"

lib/baes/actions/build_tree.rb

@@ -36,9 +36,11 @@ def find_root_branch(branches)
     end
 
     def generate_branches
-      git.branch_names.map do |branch_name|
-        Baes::Branch.new(branch_name)
+      branches = Baes::BranchCollection.new
+      git.branch_names.each do |branch_name|
+        branches << Baes::Branch.new(branch_name)
       end
+      branches
     end
 
     def prune(branch)

lib/baes/branch_collection.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+# class to encapsulate a collection of branches
+class Baes::BranchCollection
+  attr_accessor :branches
+
+  def initialize
+    self.branches = []
+  end
+
+  # add a branch
+  def <<(branch)
+    branches << branch
+  end
+
+  # find a branch
+  def find(&block)
+    branches.find(&block)
+  end
+
+  # iterate over each branch with object
+  def each_with_object(obj, &block)
+    branches.each_with_object(obj, &block)
+  end
+
+  # iterate over each branch
+  def each(&block)
+    branches.each(&block)
+  end
+
+  # return the first branch
+  def first
+    branches.first
+  end
+
+  # return a branch by index
+  def [](index)
+    branches[index]
+  end
+end