Only exclude commit authors in merge request approvers

With https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9007, anyone
who rebases or amends a commit in a merge request will be tagged as a
committer, even if there were no changes. This is surprising behavior
and prevents reviewers from even touching a merge request.

Instead, we loosen the restriction to look only at the commit authors.

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/9787

app/models/commit_collection.rb

@@ -20,8 +20,8 @@ class CommitCollection
     commits.each(&block)
   end
 
-  def committers
-    emails = without_merge_commits.map(&:committer_email).uniq
+  def authors
+    emails = without_merge_commits.map(&:author_email).uniq
 
     User.by_any_email(emails)
   end

app/models/merge_request.rb

@@ -288,12 +288,12 @@ class MergeRequest < ActiveRecord::Base
     work_in_progress?(title) ? title : "WIP: #{title}"
   end
 
-  def committers
-    @committers ||= commits.committers
+  def commit_authors
+    @commit_authors ||= commits.authors
   end
 
   def authors
-    User.from_union([committers, User.where(id: self.author_id)])
+    User.from_union([commit_authors, User.where(id: self.author_id)])
   end
 
   # Verifies if title has changed not taking into account WIP prefix

doc/user/project/merge_requests/merge_request_approvals.md

@@ -52,8 +52,8 @@ A group can also be added as an approver. [In the future](https://gitlab.com/git
 group approvers will be restricted.
 
 If a user is added as an individual approver and is also part of a group approver,
-then that user is just counted once. The merge request author and users that have committed
-to the merge request do not count as eligible approvers,
+then that user is just counted once. The merge request author and users who have authored
+commits in the merge request do not count as eligible approvers,
 unless [self-approval] is explicitly enabled on the project settings.
 
 ### Implicit approvers

spec/models/commit_collection_spec.rb

@@ -12,26 +12,26 @@ describe CommitCollection do
     end
   end
 
-  describe '.committers' do
+  describe '.authors' do
     it 'returns a relation of users when users are found' do
-      user = create(:user, email: commit.committer_email.upcase)
+      user = create(:user, email: commit.author_email.upcase)
       collection = described_class.new(project, [commit])
 
-      expect(collection.committers).to contain_exactly(user)
+      expect(collection.authors).to contain_exactly(user)
     end
 
-    it 'returns empty array when committers cannot be found' do
+    it 'returns empty array when authors cannot be found' do
       collection = described_class.new(project, [commit])
 
-      expect(collection.committers).to be_empty
+      expect(collection.authors).to be_empty
     end
 
     it 'excludes authors of merge commits' do
       commit = project.commit("60ecb67744cb56576c30214ff52294f8ce2def98")
-      create(:user, email: commit.committer_email.upcase)
+      create(:user, email: commit.author_email.upcase)
       collection = described_class.new(project, [commit])
 
-      expect(collection.committers).to be_empty
+      expect(collection.authors).to be_empty
     end
   end
 

spec/models/merge_request_spec.rb

@@ -1024,23 +1024,23 @@ describe MergeRequest do
     end
   end
 
-  describe '#committers' do
-    it 'returns all the committers of every commit in the merge request' do
-      users = subject.commits.map(&:committer_email).uniq.map do |email|
+  describe '#commit_authors' do
+    it 'returns all the authors of every commit in the merge request' do
+      users = subject.commits.map(&:author_email).uniq.map do |email|
         create(:user, email: email)
       end
 
-      expect(subject.committers).to match_array(users)
+      expect(subject.commit_authors).to match_array(users)
     end
 
-    it 'returns an empty array if no committer is associated with a user' do
-      expect(subject.committers).to be_empty
+    it 'returns an empty array if no author is associated with a user' do
+      expect(subject.commit_authors).to be_empty
     end
   end
 
   describe '#authors' do
-    it 'returns a list with all the committers in the merge request and author' do
-      users = subject.commits.map(&:committer_email).uniq.map do |email|
+    it 'returns a list with all the commit authors in the merge request and author' do
+      users = subject.commits.map(&:author_email).uniq.map do |email|
         create(:user, email: email)
       end