Fix pagination headers for repository commits api endpoint

changelogs/unreleased/13605-add-pagination-headers-for-repository-commits-api-endpoint.yml

+---
+title: Fix pagination headers for repository commits api endpoint
+merge_request:
+author: George Andrinopoulos

lib/api/commits.rb

@@ -24,7 +24,7 @@ module API
       end
       get ":id/repository/commits" do
         ref = params[:ref_name] || user_project.try(:default_branch) || 'master'
-        offset = params[:page] * params[:per_page]
+        offset = (params[:page] - 1) * params[:per_page]
         commits = user_project.repository.commits(ref,
                                                   path: params[:path],
@@ -33,8 +33,7 @@ module API
                                                   after: params[:since],
                                                   before: params[:until])
-        commit_count = user_project.repository.commit_count_for_ref(ref)
-        paginated_commits = Kaminari.paginate_array(commits, total_count: commit_count)
+        paginated_commits = Kaminari.paginate_array(commits, total_count: commits.size)
         present paginate(paginated_commits), with: Entities::RepoCommit
       end

lib/gitlab/git/repository.rb

@@ -292,7 +292,6 @@ module Gitlab
         }
         options = default_options.merge(options)
-        options[:limit] ||= 0
         options[:offset] ||= 0
         actual_ref = options[:ref] || root_ref
         begin
@@ -354,6 +353,16 @@ module Gitlab
         lines.map! { |c| Rugged::Commit.new(rugged, c.strip) }
       end
+      def count_commits(options)
+        cmd = %W(#{Gitlab.config.git.bin_path} --git-dir=#{path} rev-list)
+        cmd += %W(--after=#{options[:after].iso8601}) if options[:after]
+        cmd += %W(--before=#{options[:before].iso8601}) if options[:before]
+        cmd += %W(--count #{options[:ref]})
+        cmd += %W(-- #{options[:path]}) if options[:path].present?
+        raw_output = IO.popen(cmd) {|io| io.read }
+        raw_output.to_i
+      end
+
       def sha_from_ref(ref)
         rev_parse_target(ref).oid
       end

spec/lib/gitlab/git/repository_spec.rb

@@ -824,6 +824,35 @@ describe Gitlab::Git::Repository, seed_helper: true do
     it { is_expected.to eq(17) }
   end
+  describe '#count_commits' do
+    context 'with after timestamp' do
+      options = { ref: 'master', limit: nil, after: Time.iso8601('2013-03-03T20:15:01+00:00') }
+      it 'returns the number of commits after timestamp' do
+        commits = repository.log(options)
+
+        expect(repository.count_commits(options)).to eq(commits.size)
+      end
+    end
+
+    context 'with before timestamp' do
+      options = { ref: 'feature', limit: nil, before: Time.iso8601('2015-03-03T20:15:01+00:00') }
+      it 'returns the number of commits after timestamp' do
+        commits = repository.log(options)
+
+        expect(repository.count_commits(options)).to eq(commits.size)
+      end
+    end
+
+    context 'with path' do
+      options = { ref: 'master', limit: nil, path: "encoding" }
+      it 'returns the number of commits with path ' do
+        commits = repository.log(options)
+
+        expect(repository.count_commits(options)).to eq(commits.size)
+      end
+    end
+  end
+
   describe "branch_names_contains" do
     subject { repository.branch_names_contains(SeedRepo::LastCommit::ID) }