73 lines
2.7 KiB
Ruby
73 lines
2.7 KiB
Ruby
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# frozen_string_literal: true
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module Projects
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module Forks
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# Class for calculating the divergence of a fork with the source project
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class DivergenceCounts
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LATEST_COMMITS_COUNT = 10
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EXPIRATION_TIME = 8.hours
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def initialize(project, ref)
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@project = project
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@fork_repo = project.repository
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@source_repo = project.fork_source.repository
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@ref = ref
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end
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def counts
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ahead, behind = divergence_counts
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{ ahead: ahead, behind: behind }
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end
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private
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attr_reader :project, :fork_repo, :source_repo, :ref
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def cache_key
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@cache_key ||= ['project_forks', project.id, ref, 'divergence_counts']
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end
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def divergence_counts
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fork_sha = fork_repo.commit(ref).sha
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source_sha = source_repo.commit.sha
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cached_source_sha, cached_fork_sha, counts = Rails.cache.read(cache_key)
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return counts if cached_source_sha == source_sha && cached_fork_sha == fork_sha
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counts = calculate_divergence_counts(fork_sha, source_sha)
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Rails.cache.write(cache_key, [source_sha, fork_sha, counts], expires_in: EXPIRATION_TIME)
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counts
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end
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def calculate_divergence_counts(fork_sha, source_sha)
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# If the upstream latest commit exists in the fork repo, then
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# it's possible to calculate divergence counts within the fork repository.
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return fork_repo.diverging_commit_count(fork_sha, source_sha) if fork_repo.commit(source_sha)
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# Otherwise, we need to find a commit that exists both in the fork and upstream
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# in order to use this commit as a base for calculating divergence counts.
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# Considering the fact that a user usually creates a fork to contribute to the upstream,
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# it is expected that they have a limited number of commits ahead of upstream.
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# Let's take the latest N commits and check their existence upstream.
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last_commits_shas = fork_repo.commits(ref, limit: LATEST_COMMITS_COUNT).map(&:sha)
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existence_hash = source_repo.check_objects_exist(last_commits_shas)
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first_matched_commit_sha = last_commits_shas.find { |sha| existence_hash[sha] }
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# If we can't find such a commit, we return early and tell the user that the branches
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# have diverged and action is required.
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return unless first_matched_commit_sha
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# Otherwise, we use upstream to calculate divergence counts from the matched commit
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ahead, behind = source_repo.diverging_commit_count(first_matched_commit_sha, source_sha)
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# And add the number of commits a fork is ahead of the first matched commit
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ahead += last_commits_shas.index(first_matched_commit_sha)
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[ahead, behind]
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end
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end
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end
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end
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