diff options
Diffstat (limited to 'app/models/projects/forks')
-rw-r--r-- | app/models/projects/forks/divergence_counts.rb | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/app/models/projects/forks/divergence_counts.rb b/app/models/projects/forks/divergence_counts.rb new file mode 100644 index 00000000000..7d630b00083 --- /dev/null +++ b/app/models/projects/forks/divergence_counts.rb @@ -0,0 +1,72 @@ +# frozen_string_literal: true + +module Projects + module Forks + # Class for calculating the divergence of a fork with the source project + class DivergenceCounts + LATEST_COMMITS_COUNT = 10 + EXPIRATION_TIME = 8.hours + + def initialize(project, ref) + @project = project + @fork_repo = project.repository + @source_repo = project.fork_source.repository + @ref = ref + end + + def counts + ahead, behind = divergence_counts + + { ahead: ahead, behind: behind } + end + + private + + attr_reader :project, :fork_repo, :source_repo, :ref + + def cache_key + @cache_key ||= ['project_forks', project.id, ref, 'divergence_counts'] + end + + def divergence_counts + fork_sha = fork_repo.commit(ref).sha + source_sha = source_repo.commit.sha + + cached_source_sha, cached_fork_sha, counts = Rails.cache.read(cache_key) + return counts if cached_source_sha == source_sha && cached_fork_sha == fork_sha + + counts = calculate_divergence_counts(fork_sha, source_sha) + + Rails.cache.write(cache_key, [source_sha, fork_sha, counts], expires_in: EXPIRATION_TIME) + + counts + end + + def calculate_divergence_counts(fork_sha, source_sha) + # If the upstream latest commit exists in the fork repo, then + # it's possible to calculate divergence counts within the fork repository. + return fork_repo.diverging_commit_count(fork_sha, source_sha) if fork_repo.commit(source_sha) + + # Otherwise, we need to find a commit that exists both in the fork and upstream + # in order to use this commit as a base for calculating divergence counts. + # Considering the fact that a user usually creates a fork to contribute to the upstream, + # it is expected that they have a limited number of commits ahead of upstream. + # Let's take the latest N commits and check their existence upstream. + last_commits_shas = fork_repo.commits(ref, limit: LATEST_COMMITS_COUNT).map(&:sha) + existence_hash = source_repo.check_objects_exist(last_commits_shas) + first_matched_commit_sha = last_commits_shas.find { |sha| existence_hash[sha] } + + # If we can't find such a commit, we return early and tell the user that the branches + # have diverged and action is required. + return unless first_matched_commit_sha + + # Otherwise, we use upstream to calculate divergence counts from the matched commit + ahead, behind = source_repo.diverging_commit_count(first_matched_commit_sha, source_sha) + # And add the number of commits a fork is ahead of the first matched commit + ahead += last_commits_shas.index(first_matched_commit_sha) + + [ahead, behind] + end + end + end +end |