Cache various Repository Git operations

This caches the output of the following methods:

* Repository#empty?
* Repository#has_visible_content?
* Repository#root_ref

The cache for Repository#has_visible_content? is flushed whenever a
commit is pushed to a new branch or an existing branch is removed.
The cache for Repository#root_ref is only flushed whenever a user
changes the default branch of a project. The cache for Repository#empty?
is never explicitly flushed as there's no need for it.

1 files changed, 19 insertions, 3 deletions

diff --git a/app/models/repository.rb b/app/models/repository.rb
index e813c946bc1..27bdbac3e52 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -44,7 +44,9 @@ class Repository
   end
 
   def empty?
-    raw_repository.empty?
+    return @empty unless @empty.nil?
+
+    @empty = cache.fetch(:empty?) { raw_repository.empty? }
   end
 
   #
@@ -57,7 +59,11 @@ class Repository
   # This method return true if repository contains some content visible in project page.
   #
   def has_visible_content?
-    raw_repository.branch_count > 0
+    return @has_visible_content unless @has_visible_content.nil?
+
+    @has_visible_content = cache.fetch(:has_visible_content?) do
+      raw_repository.branch_count > 0
+    end
   end
 
   def commit(id = 'HEAD')
@@ -243,6 +249,16 @@ class Repository
     end
   end
 
+  def expire_root_ref_cache
+    cache.expire(:root_ref)
+    @root_ref = nil
+  end
+
+  def expire_has_visible_content_cache
+    cache.expire(:has_visible_content?)
+    @has_visible_content = nil
+  end
+
   def rebuild_cache
     cache_keys.each do |key|
       cache.expire(key)
@@ -480,7 +496,7 @@ class Repository
   end
 
   def root_ref
-    @root_ref ||= raw_repository.root_ref
+    @root_ref ||= cache.fetch(:root_ref) { raw_repository.root_ref }
   end
 
   def commit_dir(user, path, message, branch)