Merge branch 'undo-revert-of-4892' into 'master' 19396-api-allow-admin-owner-to-set-timestamp-when-changing-issue-state

Revert "Revert "Merge branch '18193-developers-can-merge' into 'master'""

## What does this MR do?

Reverts the revert of !4892 which lacked an EE MR at the time. This has been done in gitlab-org/gitlab-ee!564.

## What are the relevant issue numbers?

Closes #19872.

See merge request !5310

3 files changed, 19 insertions, 7 deletions

diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 157901378d3..471e32f3b60 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -552,7 +552,13 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def can_be_merged_by?(user)
-    ::Gitlab::GitAccess.new(user, project, 'web').can_push_to_branch?(target_branch)
+    access = ::Gitlab::UserAccess.new(user, project: project)
+    access.can_push_to_branch?(target_branch) || access.can_merge_to_branch?(target_branch)
+  end
+
+  def can_be_merged_via_command_line_by?(user)
+    access = ::Gitlab::UserAccess.new(user, project: project)
+    access.can_push_to_branch?(target_branch)
   end
 
   def mergeable_ci_state?
diff --git a/app/models/project.rb b/app/models/project.rb
index 1cdf22f6a51..a805f5d97bc 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -838,6 +838,10 @@ class Project < ActiveRecord::Base
     protected_branches.matching(branch_name).any?(&:developers_can_push)
   end
 
+  def developers_can_merge_to_protected_branch?(branch_name)
+    protected_branches.matching(branch_name).any?(&:developers_can_merge)
+  end
+
   def forked?
     !(forked_project_link.nil? || forked_project_link.forked_from_project.nil?)
   end
diff --git a/app/models/repository.rb b/app/models/repository.rb
index 5b670cb4b8f..09487b62f98 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -769,9 +769,9 @@ class Repository
     end
   end
 
-  def merge(user, source_sha, target_branch, options = {})
-    our_commit = rugged.branches[target_branch].target
-    their_commit = rugged.lookup(source_sha)
+  def merge(user, merge_request, options = {})
+    our_commit = rugged.branches[merge_request.target_branch].target
+    their_commit = rugged.lookup(merge_request.diff_head_sha)
 
     raise "Invalid merge target" if our_commit.nil?
     raise "Invalid merge source" if their_commit.nil?
@@ -779,14 +779,16 @@ class Repository
     merge_index = rugged.merge_commits(our_commit, their_commit)
     return false if merge_index.conflicts?
 
-    commit_with_hooks(user, target_branch) do |ref|
+    commit_with_hooks(user, merge_request.target_branch) do |tmp_ref|
       actual_options = options.merge(
         parents: [our_commit, their_commit],
         tree: merge_index.write_tree(rugged),
-        update_ref: ref
+        update_ref: tmp_ref
       )
 
-      Rugged::Commit.create(rugged, actual_options)
+      commit_id = Rugged::Commit.create(rugged, actual_options)
+      merge_request.update(in_progress_merge_commit_sha: commit_id)
+      commit_id
     end
   end