Tests: Implement scenario where .sync.yml is changed between two runs

This commit implements the scenario described at voxpupuli#192.

features/update/dot_sync.feature

@@ -0,0 +1,52 @@
+Feature: Update using a `.sync.yml` file
+  ModuleSync needs to apply templates according to `.sync.yml` content
+
+  Scenario: Updating a module with a .sync.yml file
+    Given a basic setup with a puppet module "puppet-test" from "fakenamespace"
+    And a file named "config_defaults.yml" with:
+      """
+      ---
+      :global:
+        variable: 'global'
+      template_with_specific_config:
+        variable: 'specific'
+      """
+    And a file named "moduleroot/template_with_specific_config.erb" with:
+      """
+      ---
+      <%= @configs['variable'] %>
+      """
+    And a file named "moduleroot/template_with_only_global_config.erb" with:
+      """
+      ---
+      <%= @configs['variable'] %>
+      """
+    And the puppet module "puppet-test" from "fakenamespace" has a branch named "target"
+    And the puppet module "puppet-test" from "fakenamespace" has, in branch "target", a file named ".sync.yml" with:
+      """
+      ---
+      :global:
+        variable: 'overwritten by globally defined value in .sync.yml'
+      template_with_specific_config:
+        variable: 'overwritten by file-specific defined value in .sync.yml'
+      """
+    When I successfully run `msync update --message 'Apply ModuleSync templates to target source code' --branch 'target'`
+    Then the file named "modules/fakenamespace/puppet-test/template_with_specific_config" should contain:
+      """
+      overwritten by file-specific defined value in .sync.yml
+      """
+    And the puppet module "puppet-test" from "fakenamespace" should have 1 commit made by "Aruba"
+    When the puppet module "puppet-test" from "fakenamespace" has, in branch "target", a file named ".sync.yml" with:
+      """
+      ---
+      :global:
+        variable: 'overwritten by globally defined value in .sync.yml'
+      template_with_specific_config:
+        variable: 'overwritten by newly file-specific defined value in .sync.yml'
+      """
+    And I successfully run `msync update --message 'Apply ModuleSync templates to target source code' --branch 'target'`
+    Then the file named "modules/fakenamespace/puppet-test/template_with_specific_config" should contain:
+      """
+      overwritten by newly file-specific defined value in .sync.yml
+      """
+    And the puppet module "puppet-test" from "fakenamespace" should have 2 commits made by "Aruba"