Merge branch 'expand-git-instrumentation' into 'master'

Expand Git instrumentation

This instruments some extra `Gitlab::Git` code as well as a collection of `Rugged` constants.

See merge request !2664

config/initializers/metrics.rb

@@ -49,12 +49,14 @@ if Gitlab::Metrics.enabled?
     config.instrument_instance_methods(Gitlab::Shell)
 
     config.instrument_methods(Gitlab::Git)
-    config.instrument_instance_methods(Gitlab::Git::Repository)
 
     Gitlab::Git.constants.each do |name|
       const = Gitlab::Git.const_get(name)
 
-      config.instrument_methods(const) if const.is_a?(Module)
+      next unless const.is_a?(Module)
+
+      config.instrument_methods(const)
+      config.instrument_instance_methods(const)
     end
 
     Dir[Rails.root.join('app', 'finders', '*.rb')].each do |path|
@@ -62,6 +64,16 @@ if Gitlab::Metrics.enabled?
 
       config.instrument_instance_methods(const)
     end
+
+    [
+      :Blame, :Branch, :BranchCollection, :Blob, :Commit, :Diff, :Repository,
+      :Tag, :TagCollection, :Tree
+    ].each do |name|
+      const = Rugged.const_get(name)
+
+      config.instrument_methods(const)
+      config.instrument_instance_methods(const)
+    end
   end
 
   GC::Profiler.enable