1 files changed, 41 insertions, 31 deletions

diff --git a/lib/gitlab/merge_requests/commit_message_generator.rb b/lib/gitlab/merge_requests/commit_message_generator.rb
index 0e9ec6f5cb3..0515c17fe5d 100644
--- a/lib/gitlab/merge_requests/commit_message_generator.rb
+++ b/lib/gitlab/merge_requests/commit_message_generator.rb
@@ -2,8 +2,9 @@
 module Gitlab
   module MergeRequests
     class CommitMessageGenerator
-      def initialize(merge_request:)
+      def initialize(merge_request:, current_user:)
         @merge_request = merge_request
+        @current_user = @merge_request.metrics&.merged_by || @merge_request.merge_user || current_user
       end
 
       def merge_message
@@ -15,57 +16,66 @@ module Gitlab
       def squash_message
         return unless @merge_request.target_project.squash_commit_template.present?
 
-        replace_placeholders(@merge_request.target_project.squash_commit_template)
+        replace_placeholders(@merge_request.target_project.squash_commit_template, squash: true)
       end
 
       private
 
       attr_reader :merge_request
+      attr_reader :current_user
 
       PLACEHOLDERS = {
-        'source_branch' => ->(merge_request) { merge_request.source_branch.to_s },
-        'target_branch' => ->(merge_request) { merge_request.target_branch.to_s },
-        'title' => ->(merge_request) { merge_request.title },
-        'issues' => ->(merge_request) do
-          return "" if merge_request.visible_closing_issues_for.blank?
+        'source_branch' => ->(merge_request, _, _) { merge_request.source_branch.to_s },
+        'target_branch' => ->(merge_request, _, _) { merge_request.target_branch.to_s },
+        'title' => ->(merge_request, _, _) { merge_request.title },
+        'issues' => ->(merge_request, _, _) do
+          return if merge_request.visible_closing_issues_for.blank?
 
           closes_issues_references = merge_request.visible_closing_issues_for.map do |issue|
             issue.to_reference(merge_request.target_project)
           end
           "Closes #{closes_issues_references.to_sentence}"
         end,
-        'description' => ->(merge_request) { merge_request.description.presence || '' },
-        'reference' => ->(merge_request) { merge_request.to_reference(full: true) },
-        'first_commit' => -> (merge_request) { merge_request.first_commit&.safe_message&.strip.presence || '' },
-        'first_multiline_commit' => -> (merge_request) { merge_request.first_multiline_commit&.safe_message&.strip.presence || merge_request.title }
+        'description' => ->(merge_request, _, _) { merge_request.description },
+        'reference' => ->(merge_request, _, _) { merge_request.to_reference(full: true) },
+        'first_commit' => -> (merge_request, _, _) { merge_request.first_commit&.safe_message&.strip },
+        'first_multiline_commit' => -> (merge_request, _, _) { merge_request.first_multiline_commit&.safe_message&.strip.presence || merge_request.title },
+        'url' => ->(merge_request, _, _) { Gitlab::UrlBuilder.build(merge_request) },
+        'approved_by' => ->(merge_request, _, _) { merge_request.approved_by_users.map { |user| "Approved-by: #{user.name} <#{user.commit_email_or_default}>" }.join("\n") },
+        'merged_by' => ->(_, user, _) { "#{user&.name} <#{user&.commit_email_or_default}>" },
+        'co_authored_by' => ->(merge_request, merged_by, squash) do
+          commit_author = squash ? merge_request.author : merged_by
+          merge_request.recent_commits
+                       .to_h { |commit| [commit.author_email, commit.author_name] }
+                       .except(commit_author&.commit_email_or_default)
+                       .map { |author_email, author_name| "Co-authored-by: #{author_name} <#{author_email}>" }
+                       .join("\n")
+        end
       }.freeze
 
-      PLACEHOLDERS_REGEX = Regexp.union(PLACEHOLDERS.keys.map do |key|
-        Regexp.new(Regexp.escape(key))
-      end).freeze
-
-      BLANK_PLACEHOLDERS_REGEXES = (PLACEHOLDERS.map do |key, value|
-        [key, Regexp.new("[\n\r]+%{#{Regexp.escape(key)}}$")]
-      end).to_h.freeze
+      PLACEHOLDERS_COMBINED_REGEX = /%{(#{Regexp.union(PLACEHOLDERS.keys)})}/.freeze
 
-      def replace_placeholders(message)
-        # convert CRLF to LF
+      def replace_placeholders(message, squash: false)
+        # Convert CRLF to LF.
         message = message.delete("\r")
 
-        # Remove placeholders that correspond to empty values and are the last word in the line
-        # along with all whitespace characters preceding them.
-        # This allows us to recreate previous default merge commit message behaviour - we skipped new line character
-        # before empty description and before closed issues when none were present.
-        PLACEHOLDERS.each do |key, value|
-          unless value.call(merge_request).present?
-            message = message.gsub(BLANK_PLACEHOLDERS_REGEXES[key], '')
-          end
+        used_variables = message.scan(PLACEHOLDERS_COMBINED_REGEX).map { |value| value[0] }.uniq
+        values = used_variables.to_h do |variable_name|
+          ["%{#{variable_name}}", PLACEHOLDERS[variable_name].call(merge_request, current_user, squash)]
         end
+        names_of_empty_variables = values.filter_map { |name, value| name if value.blank? }
 
-        Gitlab::StringPlaceholderReplacer
-          .replace_string_placeholders(message, PLACEHOLDERS_REGEX) do |key|
-          PLACEHOLDERS[key].call(merge_request)
+        # Remove lines that contain empty variable placeholder and nothing else.
+        if names_of_empty_variables.present?
+          # If there is blank line or EOF after it, remove blank line before it as well.
+          message = message.gsub(/\n\n#{Regexp.union(names_of_empty_variables)}(\n\n|\Z)/, '\1')
+          # Otherwise, remove only the line it is in.
+          message = message.gsub(/^#{Regexp.union(names_of_empty_variables)}\n/, '')
         end
+        # Substitute all variables with their values.
+        message = message.gsub(Regexp.union(values.keys), values) if values.present?
+
+        message
       end
     end
   end