Moved cache expiration code to Repository hooks

This keeps all the cache expiration code in a single file/class instead
of spreading it all across the codebase.

app/models/project.rb

@@ -801,10 +801,7 @@ class Project < ActiveRecord::Base
   end
 
   def change_head(branch)
-    # Cached divergent commit counts are based on repository head
-    repository.expire_branch_cache
-    repository.expire_root_ref_cache
-
+    repository.before_change_head
     gitlab_shell.update_repository_head(self.path_with_namespace, branch)
     reload_default_branch
   end

app/models/repository.rb

@@ -307,6 +307,44 @@ class Repository
     cache.expire(:branch_names)
   end
 
+  # Runs code just before a repository is deleted.
+  def before_delete
+    # FIXME: a repository not existing shouldn't prevent us from flushing caches.
+    expire_all_caches! if exists?
+  end
+
+  # Runs code just before the HEAD of a repository is changed.
+  def before_change_head
+    # Cached divergent commit counts are based on repository head
+    expire_branch_cache
+    expire_root_ref_cache
+  end
+
+  # Runs code before creating a new tag.
+  def before_create_tag
+    expire_cache
+  end
+
+  # Runs code after a repository has been forked/imported.
+  def after_import
+    expire_emptiness_caches
+  end
+
+  # Runs code after a new commit has been pushed.
+  def after_push_commit(branch_name)
+    expire_cache(branch_name)
+  end
+
+  # Runs code after a new branch has been created.
+  def after_create_branch
+    expire_has_visible_content_cache
+  end
+
+  # Runs code after an existing branch has been removed.
+  def after_remove_branch
+    expire_has_visible_content_cache
+  end
+
   def method_missing(m, *args, &block)
     if m == :lookup && !block_given?
       lookup_cache[m] ||= {}

app/services/git_push_service.rb

@@ -16,13 +16,13 @@ class GitPushService < BaseService
   #  5. Executes the project's services
   #
   def execute
-    @project.repository.expire_cache(branch_name)
+    @project.repository.after_push_commit(branch_name)
 
     if push_remove_branch?
-      @project.repository.expire_has_visible_content_cache
+      @project.repository.after_remove_branch
       @push_commits = []
     elsif push_to_new_branch?
-      @project.repository.expire_has_visible_content_cache
+      @project.repository.after_create_branch
 
       # Re-find the pushed commits.
       if is_default_branch?

app/services/git_tag_push_service.rb

@@ -2,7 +2,7 @@ class GitTagPushService
   attr_accessor :project, :user, :push_data
 
   def execute(project, user, oldrev, newrev, ref)
-    project.repository.expire_cache
+    project.repository.before_create_tag
 
     @project, @user = project, user
     @push_data = build_push_data(oldrev, newrev, ref)

app/services/projects/destroy_service.rb

@@ -76,11 +76,9 @@ module Projects
     end
 
     def flush_caches(project, wiki_path)
-      project.repository.expire_all_caches! if project.repository.exists?
+      project.repository.before_delete
 
-      wiki_repo = Repository.new(wiki_path, project)
-
-      wiki_repo.expire_all_caches! if wiki_repo.exists?
+      Repository.new(wiki_path, project).before_delete
     end
   end
 end

app/workers/repository_fork_worker.rb

@@ -27,7 +27,7 @@ class RepositoryForkWorker
       return
     end
 
-    project.repository.expire_emptiness_caches
+    project.repository.after_import
     project.import_finish
   end
 end

app/workers/repository_import_worker.rb

@@ -18,7 +18,7 @@ class RepositoryImportWorker
       return
     end
 
-    project.repository.expire_emptiness_caches
+    project.repository.after_import
     project.import_finish
   end
 end