1 files changed, 27 insertions, 7 deletions
diff --git a/lib/gitlab/ci/build/rules/rule/clause/changes.rb b/lib/gitlab/ci/build/rules/rule/clause/changes.rb
index 1bcd87c9d93..1034f5eacef 100644
--- a/lib/gitlab/ci/build/rules/rule/clause/changes.rb
+++ b/lib/gitlab/ci/build/rules/rule/clause/changes.rb
@@ -11,10 +11,12 @@ module Gitlab
         end
 
         def satisfied_by?(pipeline, context)
-          return true unless pipeline&.modified_paths
+          modified_paths = find_modified_paths(pipeline)
+
+          return true unless modified_paths
 
           expanded_globs = expand_globs(context)
-          pipeline.modified_paths.any? do |path|
+          modified_paths.any? do |path|
             expanded_globs.any? do |glob|
               File.fnmatch?(glob, path, File::FNM_PATHNAME | File::FNM_DOTMATCH | File::FNM_EXTGLOB)
             end
@@ -33,13 +35,31 @@ module Gitlab
 
         def paths
           strong_memoize(:paths) do
-            if @globs.is_a?(Array)
-              @globs
-            else
-              Array(@globs[:paths])
-            end
+            Array(@globs[:paths])
           end
         end
+
+        def find_modified_paths(pipeline)
+          return unless pipeline
+          return pipeline.modified_paths unless ::Feature.enabled?(:ci_rules_changes_compare, pipeline.project)
+
+          compare_to_sha = find_compare_to_sha(pipeline)
+
+          if compare_to_sha
+            pipeline.modified_paths_since(compare_to_sha)
+          else
+            pipeline.modified_paths
+          end
+        end
+
+        def find_compare_to_sha(pipeline)
+          return unless @globs.include?(:compare_to)
+
+          commit = pipeline.project.commit(@globs[:compare_to])
+          raise Rules::Rule::Clause::ParseError, 'rules:changes:compare_to is not a valid ref' unless commit
+
+          commit.sha
+        end
       end
     end
   end