Revert "Merge branch 'remove-rugged-walk' into 'master'"

This reverts merge request !16525

lib/gitlab/git/repository.rb

@@ -490,7 +490,11 @@ module Gitlab
           return []
         end
 
-        log_by_shell(sha, options)
+        if log_using_shell?(options)
+          log_by_shell(sha, options)
+        else
+          log_by_walk(sha, options)
+        end
       end
 
       def count_commits(options)
@@ -1517,6 +1521,27 @@ module Gitlab
         end
       end
 
+      def log_using_shell?(options)
+        options[:path].present? ||
+          options[:disable_walk] ||
+          options[:skip_merges] ||
+          options[:after] ||
+          options[:before]
+      end
+
+      def log_by_walk(sha, options)
+        walk_options = {
+          show: sha,
+          sort: Rugged::SORT_NONE,
+          limit: options[:limit],
+          offset: options[:offset]
+        }
+        Rugged::Walker.walk(rugged, walk_options).to_a
+      end
+
+      # Gitaly note: JV: although #log_by_shell shells out to Git I think the
+      # complexity is such that we should migrate it as Ruby before trying to
+      # do it in Go.
       def log_by_shell(sha, options)
         limit = options[:limit].to_i
         offset = options[:offset].to_i

spec/lib/gitlab/git/repository_spec.rb

@@ -899,6 +899,44 @@ describe Gitlab::Git::Repository, seed_helper: true do
       end
     end
 
+    context "compare results between log_by_walk and log_by_shell" do
+      let(:options) { { ref: "master" } }
+      let(:commits_by_walk) { repository.log(options).map(&:id) }
+      let(:commits_by_shell) { repository.log(options.merge({ disable_walk: true })).map(&:id) }
+
+      it { expect(commits_by_walk).to eq(commits_by_shell) }
+
+      context "with limit" do
+        let(:options) { { ref: "master", limit: 1 } }
+
+        it { expect(commits_by_walk).to eq(commits_by_shell) }
+      end
+
+      context "with offset" do
+        let(:options) { { ref: "master", offset: 1 } }
+
+        it { expect(commits_by_walk).to eq(commits_by_shell) }
+      end
+
+      context "with skip_merges" do
+        let(:options) { { ref: "master", skip_merges: true } }
+
+        it { expect(commits_by_walk).to eq(commits_by_shell) }
+      end
+
+      context "with path" do
+        let(:options) { { ref: "master", path: "encoding" } }
+
+        it { expect(commits_by_walk).to eq(commits_by_shell) }
+
+        context "with follow" do
+          let(:options) { { ref: "master", path: "encoding", follow: true } }
+
+          it { expect(commits_by_walk).to eq(commits_by_shell) }
+        end
+      end
+    end
+
     context "where provides 'after' timestamp" do
       options = { after: Time.iso8601('2014-03-03T20:15:01+00:00') }