Allow commenting on individual commits inside an MR

5 files changed, 22 insertions, 2 deletions

diff --git a/app/models/concerns/discussion_on_diff.rb b/app/models/concerns/discussion_on_diff.rb
index f5cbb3becad..4b4d519f3df 100644
--- a/app/models/concerns/discussion_on_diff.rb
+++ b/app/models/concerns/discussion_on_diff.rb
@@ -32,6 +32,10 @@ module DiscussionOnDiff
     first_note.position.new_path
   end
 
+  def on_merge_request_commit?
+    for_merge_request? && commit_id.present?
+  end
+
   # Returns an array of at most 16 highlighted lines above a diff note
   def truncated_diff_lines(highlight: true)
     lines = highlight ? highlighted_diff_lines : diff_lines
diff --git a/app/models/diff_discussion.rb b/app/models/diff_discussion.rb
index 6eba87da1a1..4a65738214b 100644
--- a/app/models/diff_discussion.rb
+++ b/app/models/diff_discussion.rb
@@ -24,7 +24,11 @@ class DiffDiscussion < Discussion
     return unless for_merge_request?
     return {} if active?
 
-    noteable.version_params_for(position.diff_refs)
+    if on_merge_request_commit?
+      { commit_id: commit_id }
+    else
+      noteable.version_params_for(position.diff_refs)
+    end
   end
 
   def reply_attributes
diff --git a/app/models/diff_note.rb b/app/models/diff_note.rb
index ae5f138a920..b53d44cda95 100644
--- a/app/models/diff_note.rb
+++ b/app/models/diff_note.rb
@@ -17,6 +17,7 @@ class DiffNote < Note
   validates :noteable_type, inclusion: { in: NOTEABLE_TYPES }
   validate :positions_complete
   validate :verify_supported
+  validate :diff_refs_match_commit, if: :for_commit?
 
   before_validation :set_original_position, on: :create
   before_validation :update_position, on: :create, if: :on_text?
@@ -135,6 +136,12 @@ class DiffNote < Note
     errors.add(:position, "is invalid")
   end
 
+  def diff_refs_match_commit
+    return if self.original_position.diff_refs == self.commit.diff_refs
+
+    errors.add(:commit_id, 'does not match the diff refs')
+  end
+
   def keep_around_commits
     project.repository.keep_around(self.original_position.base_sha)
     project.repository.keep_around(self.original_position.start_sha)
diff --git a/app/models/discussion.rb b/app/models/discussion.rb
index 437df923d2d..92482a1a875 100644
--- a/app/models/discussion.rb
+++ b/app/models/discussion.rb
@@ -11,6 +11,7 @@ class Discussion
             :author,
 
             :noteable,
+            :commit_id,
             :for_commit?,
             :for_merge_request?,
 
diff --git a/app/models/note.rb b/app/models/note.rb
index 733bbbc013f..1357e75d907 100644
--- a/app/models/note.rb
+++ b/app/models/note.rb
@@ -230,10 +230,14 @@ class Note < ActiveRecord::Base
     for_personal_snippet?
   end
 
+  def commit
+    project.commit(commit_id) if commit_id.present?
+  end
+
   # override to return commits, which are not active record
   def noteable
     if for_commit?
-      @commit ||= project.commit(commit_id)
+      @commit ||= commit
     else
       super
     end