1 files changed, 37 insertions, 0 deletions
diff --git a/app/models/repository.rb b/app/models/repository.rb
index a9bf4eb4033..6ecd2d2f27e 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -175,11 +175,29 @@ class Repository
   def size
     cache.fetch(:size) { raw_repository.size }
   end
+  
+  def diverging_commit_counts(branch)
+    root_ref_hash = raw_repository.rev_parse_target(root_ref).oid
+    cache.fetch(:"diverging_commit_counts_#{branch.name}") do
+      # Rugged seems to throw a `ReferenceError` when given branch_names rather
+      # than SHA-1 hashes
+      number_commits_behind = commits_between(branch.target, root_ref_hash).size
+      number_commits_ahead = commits_between(root_ref_hash, branch.target).size
+      
+      { behind: number_commits_behind, ahead: number_commits_ahead }
+    end
+  end
 
   def cache_keys
     %i(size branch_names tag_names commit_count
        readme version contribution_guide changelog license)
   end
+  
+  def branch_cache_keys
+    branches.map do |branch|
+      :"diverging_commit_counts_#{branch.name}"
+    end
+  end
 
   def build_cache
     cache_keys.each do |key|
@@ -187,6 +205,12 @@ class Repository
         send(key)
       end
     end
+    
+    branches.each do |branch|
+      unless cache.exist?(:"diverging_commit_counts_#{branch.name}")
+        send(:diverging_commit_counts, branch)
+      end
+    end
   end
 
   def expire_tags_cache
@@ -203,6 +227,14 @@ class Repository
     cache_keys.each do |key|
       cache.expire(key)
     end
+    
+    expire_branch_cache
+  end
+  
+  def expire_branch_cache
+    branches.each do |branch|
+      cache.expire(:"diverging_commit_counts_#{branch.name}")
+    end
   end
 
   def rebuild_cache
@@ -210,6 +242,11 @@ class Repository
       cache.expire(key)
       send(key)
     end
+    
+    branches.each do |branch|
+      cache.expire(:"diverging_commit_counts_#{branch.name}")
+      diverging_commit_counts(branch)
+    end
   end
 
   def lookup_cache