Backport 'Rebase' feature from EE to CEjprovazn-rebase

When a project uses fast-forward merging strategy user has
to rebase MRs to target branch before it can be merged.
Now user can do rebase in UI by clicking 'Rebase' button
instead of doing rebase locally.

This feature was already present in EE, this is only backport
of the feature to CE. Couple of changes:
* removed rebase license check
* renamed migration (changed timestamp)

Closes #40301

2 files changed, 15 insertions, 1 deletions

diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index c39789b047d..ef58816937c 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -156,6 +156,13 @@ class MergeRequest < ActiveRecord::Base
     '!'
   end
 
+  def rebase_in_progress?
+    # The source project can be deleted
+    return false unless source_project
+
+    source_project.repository.rebase_in_progress?(id)
+  end
+
   # Use this method whenever you need to make sure the head_pipeline is synced with the
   # branch head commit, for example checking if a merge request can be merged.
   # For more information check: https://gitlab.com/gitlab-org/gitlab-ce/issues/40004
@@ -607,7 +614,7 @@ class MergeRequest < ActiveRecord::Base
 
     check_if_can_be_merged
 
-    can_be_merged?
+    can_be_merged? && !should_be_rebased?
   end
 
   def mergeable_state?(skip_ci_check: false)
diff --git a/app/models/repository.rb b/app/models/repository.rb
index b1fd981965c..4bedcbfb6a2 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -1099,6 +1099,13 @@ class Repository
     @project.repository_storage_path
   end
 
+  def rebase(user, merge_request)
+    raw.rebase(user, merge_request.id, branch: merge_request.source_branch,
+                                       branch_sha: merge_request.source_branch_sha,
+                                       remote_repository: merge_request.target_project.repository.raw,
+                                       remote_branch: merge_request.target_branch)
+  end
+
   private
 
   # TODO Generice finder, later split this on finders by Ref or Oid