Enrich commits with full data in CommitCollection

Allow incomplete commit records to load their full data from gitaly.

Commits can be based on a Hash of data retrieved from PostgreSQL, and
this data can be intentionally incomplete in order to save space.

A new method #gitaly? has been added to Gitlab::Git::Commit, which
returns true if the underlying data source of the Commit is a
Gitaly::GitCommit.

CommitCollection now has a method #enrich which replaces non-gitaly
commits in place with commits from gitaly.

CommitCollection#without_merge_commits has been updated to call this
method, as in order to determine a merge commit we need to have parent
data.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/58805

1 files changed, 30 insertions, 1 deletions

diff --git a/app/models/commit_collection.rb b/app/models/commit_collection.rb
index a9a2e9c81eb..f4e64abf362 100644
--- a/app/models/commit_collection.rb
+++ b/app/models/commit_collection.rb
@@ -28,10 +28,39 @@ class CommitCollection
 
   def without_merge_commits
     strong_memoize(:without_merge_commits) do
-      commits.reject(&:merge_commit?)
+      # `#enrich!` the collection to ensure all commits contain
+      # the necessary parent data
+      enrich!.commits.reject(&:merge_commit?)
     end
   end
 
+  def unenriched
+    commits.reject(&:gitaly_commit?)
+  end
+
+  def fully_enriched?
+    unenriched.empty?
+  end
+
+  # Batch load any commits that are not backed by full gitaly data, and
+  # replace them in the collection.
+  def enrich!
+    return self if fully_enriched?
+
+    # Batch load full Commits from the repository
+    # and map to a Hash of id => Commit
+    replacements = Hash[unenriched.map do |c|
+      [c.id, Commit.lazy(project, c.id)]
+    end.compact]
+
+    # Replace the commits, keeping the same order
+    @commits = @commits.map do |c|
+      replacements.fetch(c.id, c)
+    end
+
+    self
+  end
+
   # Sets the pipeline status for every commit.
   #
   # Setting this status ahead of time removes the need for running a query for