repository: Add new `#blobs` function to enumerate blobs

Now that the `BlobService` has support for enumerating blobs via a the
new Gitaly RPC `#list_blobs`, implement support for reading blobs via
`Repository#blobs`.

lib/gitlab/git/repository.rb

@@ -370,6 +370,20 @@ module Gitlab
         end
       end
 
+      # List blobs reachable via a set of revisions. Supports the
+      # pseudo-revisions `--not` and `--all`. Uses the minimum of
+      # GitalyClient.medium_timeout and dynamic timeout if the dynamic
+      # timeout is set, otherwise it'll always use the medium timeout.
+      def blobs(revisions, dynamic_timeout: nil)
+        revisions = revisions.reject { |rev| rev.blank? || rev == ::Gitlab::Git::BLANK_SHA }
+
+        return [] if revisions.blank?
+
+        wrapped_gitaly_errors do
+          gitaly_blob_client.list_blobs(revisions, limit: REV_LIST_COMMIT_LIMIT, dynamic_timeout: dynamic_timeout)
+        end
+      end
+
       def count_commits(options)
         options = process_count_commits_options(options.dup)
 

spec/lib/gitlab/git/repository_spec.rb

@@ -869,6 +869,71 @@ RSpec.describe Gitlab::Git::Repository, :seed_helper do
     end
   end
 
+  describe '#blobs' do
+    let_it_be(:commit_oid) { '4b4918a572fa86f9771e5ba40fbd48e1eb03e2c6' }
+
+    shared_examples 'a blob enumeration' do
+      it 'enumerates blobs' do
+        blobs = repository.blobs(revisions).to_a
+
+        expect(blobs.size).to eq(expected_blobs)
+        blobs.each do |blob|
+          expect(blob.data).to be_empty
+          expect(blob.id.size).to be(40)
+        end
+      end
+    end
+
+    context 'single revision' do
+      let(:revisions) { [commit_oid] }
+      let(:expected_blobs) { 53 }
+
+      it_behaves_like 'a blob enumeration'
+    end
+
+    context 'multiple revisions' do
+      let(:revisions) { ["^#{commit_oid}~", commit_oid] }
+      let(:expected_blobs) { 1 }
+
+      it_behaves_like 'a blob enumeration'
+    end
+
+    context 'pseudo revisions' do
+      let(:revisions) { ['master', '--not', '--all'] }
+      let(:expected_blobs) { 0 }
+
+      it_behaves_like 'a blob enumeration'
+    end
+
+    context 'blank revisions' do
+      let(:revisions) { [::Gitlab::Git::BLANK_SHA] }
+      let(:expected_blobs) { 0 }
+
+      before do
+        expect_any_instance_of(Gitlab::GitalyClient::BlobService)
+          .not_to receive(:list_blobs)
+      end
+
+      it_behaves_like 'a blob enumeration'
+    end
+
+    context 'partially blank revisions' do
+      let(:revisions) { [::Gitlab::Git::BLANK_SHA, commit_oid] }
+      let(:expected_blobs) { 53 }
+
+      before do
+        expect_next_instance_of(Gitlab::GitalyClient::BlobService) do |service|
+          expect(service)
+            .to receive(:list_blobs)
+            .with([commit_oid], kind_of(Hash))
+            .and_call_original
+        end
+      end
+
+      it_behaves_like 'a blob enumeration'
+    end
+  end
+
   describe '#count_commits_between' do
     subject { repository.count_commits_between('feature', 'master') }