Move duplicate-key method to Minidoc

We're going to remove the Indexes module.

Author: pbrisbin

Diff for: lib/minidoc.rb

@@ -103,6 +103,20 @@ def self.transaction(isolation = "mvcc")
     end
   end
 
+  # Rescue a duplicate key exception in the given block. Returns the result of
+  # the block, or +false+ if the exception was raised.
+  def self.rescue_duplicate_key_errors
+    yield
+  rescue Minidoc::DuplicateKey
+    false
+  rescue Mongo::OperationFailure => ex
+    if Minidoc::DuplicateKey.duplicate_key_exception(ex)
+      false
+    else
+      raise
+    end
+  end
+
   def self.tokumx?
     @server_info ||= connection.server_info
     @server_info.key?("tokumxVersion")

Diff for: test/duplicate_key_test.rb

@@ -0,0 +1,21 @@
+require File.expand_path('../helper', __FILE__)
+
+class DuplicateKeyTest < Minidoc::TestCase
+  def test_rescue_duplicate_key_errors_result
+    user = User.create!
+    result = Minidoc.rescue_duplicate_key_errors do
+      User.create!(name: "two")
+    end
+
+    assert_equal "two", result.name
+  end
+
+  def test_rescue_duplicate_key_errors_false
+    user = User.create!
+    result = Minidoc.rescue_duplicate_key_errors do
+      User.create!(_id: user.id, name: "two")
+    end
+
+    assert_equal false, result
+  end
+end