Merge branch 'bvl-fork-network-schema' into 'master'

Create merge requests across a fork network

Closes #20097

See merge request gitlab-org/gitlab-ce!14422

6 files changed, 54 insertions, 13 deletions

diff --git a/app/models/fork_network.rb b/app/models/fork_network.rb
new file mode 100644
index 00000000000..218e37a5312
--- /dev/null
+++ b/app/models/fork_network.rb
@@ -0,0 +1,15 @@
+class ForkNetwork < ActiveRecord::Base
+  belongs_to :root_project, class_name: 'Project'
+  has_many :fork_network_members
+  has_many :projects, through: :fork_network_members
+
+  after_create :add_root_as_member, if: :root_project
+
+  def add_root_as_member
+    projects << root_project
+  end
+
+  def find_forks_in(other_projects)
+    projects.where(id: other_projects)
+  end
+end
diff --git a/app/models/fork_network_member.rb b/app/models/fork_network_member.rb
new file mode 100644
index 00000000000..6a9b52a1ef8
--- /dev/null
+++ b/app/models/fork_network_member.rb
@@ -0,0 +1,7 @@
+class ForkNetworkMember < ActiveRecord::Base
+  belongs_to :fork_network
+  belongs_to :project
+  belongs_to :forked_from_project, class_name: 'Project'
+
+  validates :fork_network, :project, presence: true
+end
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 086226618e6..9b312f7db6c 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -403,7 +403,7 @@ class MergeRequest < ActiveRecord::Base
     return false unless for_fork?
     return true unless source_project
 
-    !source_project.forked_from?(target_project)
+    !source_project.in_fork_network_of?(target_project)
   end
 
   def reopenable?
diff --git a/app/models/namespace.rb b/app/models/namespace.rb
index e279d8dd8c5..4672881e220 100644
--- a/app/models/namespace.rb
+++ b/app/models/namespace.rb
@@ -139,7 +139,9 @@ class Namespace < ActiveRecord::Base
   end
 
   def find_fork_of(project)
-    projects.joins(:forked_project_link).find_by('forked_project_links.forked_from_project_id = ?', project.id)
+    return nil unless project.fork_network
+
+    project.fork_network.find_forks_in(projects).first
   end
 
   def lfs_enabled?
diff --git a/app/models/project.rb b/app/models/project.rb
index 608b545f99f..ad1c339ae78 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -118,11 +118,20 @@ class Project < ActiveRecord::Base
   has_one :mock_monitoring_service
   has_one :microsoft_teams_service
 
+  # TODO: replace these relations with the fork network versions
   has_one  :forked_project_link,  foreign_key: "forked_to_project_id"
   has_one  :forked_from_project,  through:   :forked_project_link
 
   has_many :forked_project_links, foreign_key: "forked_from_project_id"
   has_many :forks,                through:     :forked_project_links, source: :forked_to_project
+  # TODO: replace these relations with the fork network versions
+
+  has_one :root_of_fork_network,
+          foreign_key: 'root_project_id',
+          inverse_of: :root_project,
+          class_name: 'ForkNetwork'
+  has_one :fork_network_member
+  has_one :fork_network, through: :fork_network_member
 
   # Merge Requests for target project should be removed with it
   has_many :merge_requests, foreign_key: 'target_project_id'
@@ -1000,6 +1009,11 @@ class Project < ActiveRecord::Base
   end
 
   def forked?
+    return true if fork_network && fork_network.root_project != self
+
+    # TODO: Use only the above conditional using the `fork_network`
+    # This is the old conditional that looks at the `forked_project_link`, we
+    # fall back to this while we're migrating the new models
     !(forked_project_link.nil? || forked_project_link.forked_from_project.nil?)
   end
 
@@ -1119,8 +1133,19 @@ class Project < ActiveRecord::Base
     end
   end
 
-  def forked_from?(project)
-    forked? && project == forked_from_project
+  def forked_from?(other_project)
+    forked? && forked_from_project == other_project
+  end
+
+  def in_fork_network_of?(other_project)
+    # TODO: Remove this in a next release when all fork_networks are populated
+    # This makes sure all MergeRequests remain valid while the projects don't
+    # have a fork_network yet.
+    return true if forked_from?(other_project)
+
+    return false if fork_network.nil? || other_project.fork_network.nil?
+
+    fork_network == other_project.fork_network
   end
 
   def origin_merge_requests
diff --git a/app/models/user.rb b/app/models/user.rb
index 959738ba608..c3f115ca074 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -697,15 +697,7 @@ class User < ActiveRecord::Base
   end
 
   def fork_of(project)
-    links = ForkedProjectLink.where(
-      forked_from_project_id: project,
-      forked_to_project_id: personal_projects.unscope(:order)
-    )
-    if links.any?
-      links.first.forked_to_project
-    else
-      nil
-    end
+    namespace.find_fork_of(project)
   end
 
   def ldap_user?