Merge branch 'feature/gb/pipeline-only-except-with-modified-paths' into 'master'

Pipeline only/except for modified paths

See merge request gitlab-org/gitlab-ce!21981

app/models/ci/pipeline.rb

@@ -627,6 +627,18 @@ module Ci
       end
     end
 
+    def branch_updated?
+      strong_memoize(:branch_updated) do
+        push_details.branch_updated?
+      end
+    end
+
+    def modified_paths
+      strong_memoize(:modified_paths) do
+        push_details.modified_paths
+      end
+    end
+
     def default_branch?
       ref == project.default_branch
     end
@@ -654,6 +666,22 @@ module Ci
       Gitlab::DataBuilder::Pipeline.build(self)
     end
 
+    def push_details
+      strong_memoize(:push_details) do
+        Gitlab::Git::Push.new(project, before_sha, sha, push_ref)
+      end
+    end
+
+    def push_ref
+      if branch?
+        Gitlab::Git::BRANCH_REF_PREFIX + ref.to_s
+      elsif tag?
+        Gitlab::Git::TAG_REF_PREFIX + ref.to_s
+      else
+        raise ArgumentError, 'Invalid pipeline type!'
+      end
+    end
+
     def latest_builds_status
       return 'failed' unless yaml_errors.blank?
 

app/services/merge_requests/base_service.rb

@@ -57,10 +57,10 @@ module MergeRequests
     # Returns all origin and fork merge requests from `@project` satisfying passed arguments.
     # rubocop: disable CodeReuse/ActiveRecord
     def merge_requests_for(source_branch, mr_states: [:opened])
-      MergeRequest
+      @project.source_of_merge_requests
         .with_state(mr_states)
-        .where(source_branch: source_branch, source_project_id: @project.id)
-        .preload(:source_project) # we don't need a #includes since we're just preloading for the #select
+        .where(source_branch: source_branch)
+        .preload(:source_project) # we don't need #includes since we're just preloading for the #select
         .select(&:source_project)
     end
     # rubocop: enable CodeReuse/ActiveRecord

app/services/merge_requests/refresh_service.rb

@@ -3,17 +3,16 @@
 module MergeRequests
   class RefreshService < MergeRequests::BaseService
     def execute(oldrev, newrev, ref)
-      return true unless Gitlab::Git.branch_ref?(ref)
+      @push = Gitlab::Git::Push.new(@project, oldrev, newrev, ref)
 
-      do_execute(oldrev, newrev, ref)
+      return true unless @push.branch_push?
+
+      refresh_merge_requests!
     end
 
     private
 
-    def do_execute(oldrev, newrev, ref)
-      @oldrev, @newrev = oldrev, newrev
-      @branch_name = Gitlab::Git.ref_name(ref)
-
+    def refresh_merge_requests!
       Gitlab::GitalyClient.allow_n_plus_1_calls(&method(:find_new_commits))
       # Be sure to close outstanding MRs before reloading them to avoid generating an
       # empty diff during a manual merge
@@ -25,7 +24,7 @@ module MergeRequests
       cache_merge_requests_closing_issues
 
       # Leave a system note if a branch was deleted/added
-      if branch_added? || branch_removed?
+      if @push.branch_added? || @push.branch_removed?
         comment_mr_branch_presence_changed
       end
 
@@ -54,8 +53,10 @@ module MergeRequests
     # rubocop: disable CodeReuse/ActiveRecord
     def post_merge_manually_merged
       commit_ids = @commits.map(&:id)
-      merge_requests = @project.merge_requests.preload(:latest_merge_request_diff).opened.where(target_branch: @branch_name).to_a
-      merge_requests = merge_requests.select(&:diff_head_commit)
+      merge_requests = @project.merge_requests.opened
+        .preload(:latest_merge_request_diff)
+        .where(target_branch: @push.branch_name).to_a
+        .select(&:diff_head_commit)
 
       merge_requests = merge_requests.select do |merge_request|
         commit_ids.include?(merge_request.diff_head_sha) &&
@@ -70,24 +71,20 @@ module MergeRequests
     end
     # rubocop: enable CodeReuse/ActiveRecord
 
-    def force_push?
-      Gitlab::Checks::ForcePush.force_push?(@project, @oldrev, @newrev)
-    end
-
     # Refresh merge request diff if we push to source or target branch of merge request
     # Note: we should update merge requests from forks too
     # rubocop: disable CodeReuse/ActiveRecord
     def reload_merge_requests
       merge_requests = @project.merge_requests.opened
-        .by_source_or_target_branch(@branch_name).to_a
+        .by_source_or_target_branch(@push.branch_name).to_a
 
       # Fork merge requests
       merge_requests += MergeRequest.opened
-        .where(source_branch: @branch_name, source_project: @project)
+        .where(source_branch: @push.branch_name, source_project: @project)
         .where.not(target_project: @project).to_a
 
       filter_merge_requests(merge_requests).each do |merge_request|
-        if merge_request.source_branch == @branch_name || force_push?
+        if merge_request.source_branch == @push.branch_name || @push.force_push?
           merge_request.reload_diff(current_user)
         else
           mr_commit_ids = merge_request.commit_shas
@@ -117,7 +114,7 @@ module MergeRequests
     end
 
     def find_new_commits
-      if branch_added?
+      if @push.branch_added?
         @commits = []
 
         merge_request = merge_requests_for_source_branch.first
@@ -126,28 +123,28 @@ module MergeRequests
         begin
           # Since any number of commits could have been made to the restored branch,
           # find the common root to see what has been added.
-          common_ref = @project.repository.merge_base(merge_request.diff_head_sha, @newrev)
+          common_ref = @project.repository.merge_base(merge_request.diff_head_sha, @push.newrev)
           # If the a commit no longer exists in this repo, gitlab_git throws
           # a Rugged::OdbError. This is fixed in https://gitlab.com/gitlab-org/gitlab_git/merge_requests/52
-          @commits = @project.repository.commits_between(common_ref, @newrev) if common_ref
+          @commits = @project.repository.commits_between(common_ref, @push.newrev) if common_ref
         rescue
         end
-      elsif branch_removed?
+      elsif @push.branch_removed?
         # No commits for a deleted branch.
         @commits = []
       else
-        @commits = @project.repository.commits_between(@oldrev, @newrev)
+        @commits = @project.repository.commits_between(@push.oldrev, @push.newrev)
       end
     end
 
     # Add comment about branches being deleted or added to merge requests
     def comment_mr_branch_presence_changed
-      presence = branch_added? ? :add : :delete
+      presence = @push.branch_added? ? :add : :delete
 
       merge_requests_for_source_branch.each do |merge_request|
         SystemNoteService.change_branch_presence(
           merge_request, merge_request.project, @current_user,
-            :source, @branch_name, presence)
+          :source, @push.branch_name, presence)
       end
     end
 
@@ -164,7 +161,7 @@ module MergeRequests
 
         SystemNoteService.add_commits(merge_request, merge_request.project,
                                       @current_user, new_commits,
-                                      existing_commits, @oldrev)
+                                      existing_commits, @push.oldrev)
 
         notification_service.push_to_merge_request(merge_request, @current_user, new_commits: new_commits, existing_commits: existing_commits)
       end
@@ -195,7 +192,7 @@ module MergeRequests
     # Call merge request webhook with update branches
     def execute_mr_web_hooks
       merge_requests_for_source_branch.each do |merge_request|
-        execute_hooks(merge_request, 'update', old_rev: @oldrev)
+        execute_hooks(merge_request, 'update', old_rev: @push.oldrev)
       end
     end
 
@@ -203,7 +200,7 @@ module MergeRequests
     # `MergeRequestsClosingIssues` model (as a performance optimization).
     # rubocop: disable CodeReuse/ActiveRecord
     def cache_merge_requests_closing_issues
-      @project.merge_requests.where(source_branch: @branch_name).each do |merge_request|
+      @project.merge_requests.where(source_branch: @push.branch_name).each do |merge_request|
         merge_request.cache_merge_request_closes_issues!(@current_user)
       end
     end
@@ -215,15 +212,7 @@ module MergeRequests
 
     def merge_requests_for_source_branch(reload: false)
       @source_merge_requests = nil if reload
-      @source_merge_requests ||= merge_requests_for(@branch_name)
-    end
-
-    def branch_added?
-      Gitlab::Git.blank_ref?(@oldrev)
-    end
-
-    def branch_removed?
-      Gitlab::Git.blank_ref?(@newrev)
+      @source_merge_requests ||= merge_requests_for(@push.branch_name)
     end
   end
 end

changelogs/unreleased/feature-gb-pipeline-only-except-with-modified-paths.yml

+---
+title: Add support for pipeline only/except policy for modified paths
+merge_request: 21981
+author:
+type: added

doc/ci/yaml/README.md

@@ -387,6 +387,8 @@ except master.
 > `refs` and `kubernetes` policies introduced in GitLab 10.0
 >
 > `variables` policy introduced in 10.7
+>
+> `changes` policy [introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/19232) in 11.4
 
 CAUTION: **Warning:**
 This an _alpha_ feature, and it it subject to change at any time without
@@ -398,10 +400,15 @@ policy configuration.
 GitLab now supports both, simple and complex strategies, so it is possible to
 use an array and a hash configuration scheme.
 
-Three keys are now available: `refs`, `kubernetes` and `variables`.
+Four keys are now available: `refs`, `kubernetes` and `variables` and `changes`.
+
+### `refs` and `kubernetes`
+
 Refs strategy equals to simplified only/except configuration, whereas
 kubernetes strategy accepts only `active` keyword.
 
+### `variables`
+
 `variables` keyword is used to define variables expressions. In other words
 you can use predefined variables / project / group or
 environment-scoped variables to define an expression GitLab is going to
@@ -445,6 +452,46 @@ end-to-end:
 
 Learn more about variables expressions on [a separate page][variables-expressions].
 
+### `changes`
+
+Using `changes` keyword with `only` or `except` makes it possible to define if
+a job should be created based on files modified by a git push event.
+
+For example:
+
+```yaml
+docker build:
+  script: docker build -t my-image:$CI_COMMIT_REF_SLUG .
+  only:
+    changes:
+      - Dockerfile
+      - docker/scripts/*
+```
+
+In the scenario above, if you are pushing multiple commits to GitLab to an
+existing branch, GitLab creates and triggers `docker build` job, provided that
+one of the commits contains changes to either:
+
+- The `Dockerfile` file.
+- Any of the files inside `docker/scripts/` directory.
+
+CAUTION: **Warning:**
+There are some caveats when using this feature with new branches and tags. See
+the section below.
+
+#### Using `changes` with new branches and tags
+
+If you are pushing a **new** branch or a **new** tag to GitLab, the policy
+always evaluates to true and GitLab will create a job. This feature is not
+connected with merge requests yet, and because GitLab is creating pipelines
+before an user can create a merge request we don't know a target branch at
+this point.
+
+Without a target branch, it is not possible to know what the common ancestor is,
+thus we always create a job in that case. This feature works best for stable
+branches like `master` because in that case GitLab uses the previous commit
+that is present in a branch to compare against the latest SHA that was pushed.
+
 ## `tags`
 
 `tags` is used to select specific Runners from the list of all Runners that are

lib/gitlab/ci/build/policy/changes.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module Build
+      module Policy
+        class Changes < Policy::Specification
+          def initialize(globs)
+            @globs = Array(globs)
+          end
+
+          def satisfied_by?(pipeline, seed)
+            return true unless pipeline.branch_updated?
+
+            pipeline.modified_paths.any? do |path|
+              @globs.any? do |glob|
+                File.fnmatch?(glob, path, File::FNM_PATHNAME | File::FNM_DOTMATCH)
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/gitlab/ci/config/entry/policy.rb

@@ -25,17 +25,19 @@ module Gitlab
             include Entry::Validatable
             include Entry::Attributable
 
-            attributes :refs, :kubernetes, :variables
+            ALLOWED_KEYS = %i[refs kubernetes variables changes].freeze
+            attributes :refs, :kubernetes, :variables, :changes
 
             validations do
               validates :config, presence: true
-              validates :config, allowed_keys: %i[refs kubernetes variables]
+              validates :config, allowed_keys: ALLOWED_KEYS
               validate :variables_expressions_syntax
 
               with_options allow_nil: true do
                 validates :refs, array_of_strings_or_regexps: true
                 validates :kubernetes, allowed_values: %w[active]
                 validates :variables, array_of_strings: true
+                validates :changes, array_of_strings: true
               end
 
               def variables_expressions_syntax

lib/gitlab/git/diff_stats_collection.rb

@@ -18,6 +18,10 @@ module Gitlab
         indexed_by_path[path]
       end
 
+      def paths
+        @collection.map(&:path)
+      end
+
       private
 
       def indexed_by_path

lib/gitlab/git/push.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Git
+    class Push
+      include Gitlab::Utils::StrongMemoize
+
+      attr_reader :oldrev, :newrev
+
+      def initialize(project, oldrev, newrev, ref)
+        @project = project
+        @oldrev = oldrev.presence || Gitlab::Git::BLANK_SHA
+        @newrev = newrev.presence || Gitlab::Git::BLANK_SHA
+        @ref = ref
+      end
+
+      def branch_name
+        strong_memoize(:branch_name) do
+          Gitlab::Git.branch_name(@ref)
+        end
+      end
+
+      def branch_added?
+        Gitlab::Git.blank_ref?(@oldrev)
+      end
+
+      def branch_removed?
+        Gitlab::Git.blank_ref?(@newrev)
+      end
+
+      def branch_updated?
+        branch_push? && !branch_added? && !branch_removed?
+      end
+
+      def force_push?
+        Gitlab::Checks::ForcePush.force_push?(@project, @oldrev, @newrev)
+      end
+
+      def branch_push?
+        strong_memoize(:branch_push) do
+          Gitlab::Git.branch_ref?(@ref)
+        end
+      end
+
+      def modified_paths
+        unless branch_updated?
+          raise ArgumentError, 'Unable to calculate modified paths!'
+        end
+
+        strong_memoize(:modified_paths) do
+          @project.repository.diff_stats(@oldrev, @newrev).paths
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/ci/build/policy/changes_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Ci::Build::Policy::Changes do
+  set(:project) { create(:project) }
+
+  describe '#satisfied_by?' do
+    describe 'paths matching matching' do
+      let(:pipeline) do
+        build(:ci_empty_pipeline, project: project,
+                                  ref: 'master',
+                                  source: :push,
+                                  sha: '1234abcd',
+                                  before_sha: '0123aabb')
+      end
+
+      let(:ci_build) do
+        build(:ci_build, pipeline: pipeline, project: project, ref: 'master')
+      end
+
+      let(:seed) { double('build seed', to_resource: ci_build) }
+
+      before do
+        allow(pipeline).to receive(:modified_paths) do
+          %w[some/modified/ruby/file.rb some/other_file.txt some/.dir/file]
+        end
+      end
+
+      it 'is satisfied by matching literal path' do
+        policy = described_class.new(%w[some/other_file.txt])
+
+        expect(policy).to be_satisfied_by(pipeline, seed)
+      end
+
+      it 'is satisfied by matching simple pattern' do
+        policy = described_class.new(%w[some/*.txt])
+
+        expect(policy).to be_satisfied_by(pipeline, seed)
+      end
+
+      it 'is satisfied by matching recusive pattern' do
+        policy = described_class.new(%w[some/**/*.rb])
+
+        expect(policy).to be_satisfied_by(pipeline, seed)
+      end
+
+      it 'is satisfied by matching a pattern with a dot' do
+        policy = described_class.new(%w[some/*/file])
+
+        expect(policy).to be_satisfied_by(pipeline, seed)
+      end
+
+      it 'is not satisfied when pattern does not match path' do
+        policy = described_class.new(%w[some/*.rb])
+
+        expect(policy).not_to be_satisfied_by(pipeline, seed)
+      end
+
+      it 'is not satisfied when pattern does not match' do
+        policy = described_class.new(%w[invalid/*.md])
+
+        expect(policy).not_to be_satisfied_by(pipeline, seed)
+      end
+
+      context 'when pipelines does not run for a branch update' do
+        before do
+          pipeline.before_sha = Gitlab::Git::BLANK_SHA
+        end
+
+        it 'is always satisfied' do
+          policy = described_class.new(%w[invalid/*])
+
+          expect(policy).to be_satisfied_by(pipeline, seed)
+        end
+      end
+    end
+
+    describe 'gitaly integration' do
+      set(:project) { create(:project, :repository) }
+
+      let(:pipeline) do
+        create(:ci_empty_pipeline, project: project,
+                                   ref: 'master',
+                                   source: :push,
+                                   sha: '498214d',
+                                   before_sha: '281d3a7')
+      end
+
+      let(:build) do
+        create(:ci_build, pipeline: pipeline, project: project, ref: 'master')
+      end
+
+      let(:seed) { double('build seed', to_resource: build) }
+
+      it 'is satisfied by changes introduced by a push' do
+        policy = described_class.new(['with space/*.md'])
+
+        expect(policy).to be_satisfied_by(pipeline, seed)
+      end
+
+      it 'is not satisfied by changes that are not in the push' do
+        policy = described_class.new(%w[files/js/commit.js])
+
+        expect(policy).not_to be_satisfied_by(pipeline, seed)
+      end
+    end
+  end
+end

spec/lib/gitlab/ci/config/entry/policy_spec.rb

-require 'spec_helper'
+require 'fast_spec_helper'
+require_dependency 'active_model'
 
 describe Gitlab::Ci::Config::Entry::Policy do
   let(:entry) { described_class.new(config) }
@@ -124,6 +125,23 @@ describe Gitlab::Ci::Config::Entry::Policy do
       end
     end
 
+    context 'when specifying a valid changes policy' do
+      let(:config) { { changes: %w[some/* paths/**/*.rb] } }
+
+      it 'is a correct configuraton' do
+        expect(entry).to be_valid
+        expect(entry.value).to eq(config)
+      end
+    end
+
+    context 'when changes policy is invalid' do
+      let(:config) { { changes: [1, 2] } }
+
+      it 'returns errors' do
+        expect(entry.errors).to include /changes should be an array of strings/
+      end
+    end
+
     context 'when specifying unknown policy' do
       let(:config) { { refs: ['master'], invalid: :something } }
 

spec/lib/gitlab/ci/yaml_processor_spec.rb

@@ -1354,7 +1354,7 @@ module Gitlab
           end.to raise_error(Gitlab::Ci::YamlProcessor::ValidationError, "jobs:rspec dependencies should be an array of strings")
         end
 
-        it 'returns errors if pipeline variables expression is invalid' do
+        it 'returns errors if pipeline variables expression policy is invalid' do
           config = YAML.dump({ rspec: { script: 'test', only: { variables: ['== null'] } } })
 
           expect { Gitlab::Ci::YamlProcessor.new(config) }
@@ -1362,6 +1362,14 @@ module Gitlab
                             'jobs:rspec:only variables invalid expression syntax')
         end
 
+        it 'returns errors if pipeline changes policy is invalid' do
+          config = YAML.dump({ rspec: { script: 'test', only: { changes: [1] } } })
+
+          expect { Gitlab::Ci::YamlProcessor.new(config) }
+            .to raise_error(Gitlab::Ci::YamlProcessor::ValidationError,
+                            'jobs:rspec:only changes should be an array of strings')
+        end
+
         it 'returns errors if extended hash configuration is invalid' do
           config = YAML.dump({ rspec: { extends: 'something', script: 'test' } })
 

spec/lib/gitlab/git/diff_stats_collection_spec.rb

@@ -14,7 +14,7 @@ describe Gitlab::Git::DiffStatsCollection do
   let(:diff_stats) { [stats_a, stats_b] }
   let(:collection) { described_class.new(diff_stats) }
 
-  describe '.find_by_path' do
+  describe '#find_by_path' do
     it 'returns stats by path when found' do
       expect(collection.find_by_path('foo')).to eq(stats_a)
     end
@@ -23,4 +23,10 @@ describe Gitlab::Git::DiffStatsCollection do
       expect(collection.find_by_path('no-file')).to be_nil
     end
   end
+
+  describe '#paths' do
+    it 'returns only modified paths' do
+      expect(collection.paths).to eq %w[foo bar]
+    end
+  end
 end

spec/lib/gitlab/git/push_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Git::Push do
+  set(:project) { create(:project, :repository) }
+
+  let(:oldrev) { project.commit('HEAD~2').id }
+  let(:newrev) { project.commit.id }
+  let(:ref) { 'refs/heads/some-branch' }
+
+  subject { described_class.new(project, oldrev, newrev, ref) }
+
+  describe '#branch_name' do
+    context 'when it is a branch push' do
+      let(:ref) { 'refs/heads/my-branch' }
+
+      it 'returns branch name' do
+        expect(subject.branch_name).to eq 'my-branch'
+      end
+    end
+
+    context 'when it is a tag push' do
+      let(:ref) { 'refs/tags/my-branch' }
+
+      it 'returns nil' do
+        expect(subject.branch_name).to be_nil
+      end
+    end
+  end
+
+  describe '#branch_push?' do
+    context 'when pushing a branch ref' do
+      let(:ref) { 'refs/heads/my-branch' }
+
+      it { is_expected.to be_branch_push }
+    end
+
+    context 'when it is a tag push' do
+      let(:ref) { 'refs/tags/my-tag' }
+
+      it { is_expected.not_to be_branch_push }
+    end
+  end
+
+  describe '#branch_updated?' do
+    context 'when it is a branch push with correct old and new revisions' do
+      it { is_expected.to be_branch_updated }
+    end
+
+    context 'when it is not a branch push' do
+      let(:ref) { 'refs/tags/my-tag' }
+
+      it { is_expected.not_to be_branch_updated }
+    end
+
+    context 'when old revision is blank' do
+      let(:oldrev) { Gitlab::Git::BLANK_SHA }
+
+      it { is_expected.not_to be_branch_updated }
+    end
+
+    context 'when it is not a branch push' do
+      let(:newrev) { Gitlab::Git::BLANK_SHA }
+
+      it { is_expected.not_to be_branch_updated }
+    end
+
+    context 'when oldrev is nil' do
+      let(:oldrev) { nil }
+
+      it { is_expected.not_to be_branch_updated }
+    end
+  end
+
+  describe '#force_push?' do
+    context 'when old revision is an ancestor of the new revision' do
+      let(:oldrev) { 'HEAD~3' }
+      let(:newrev) { 'HEAD~1' }
+
+      it { is_expected.not_to be_force_push }
+    end
+
+    context 'when old revision is not an ancestor of the new revision' do
+      let(:oldrev) { 'HEAD~3' }
+      let(:newrev) { '123456' }
+
+      it { is_expected.to be_force_push }
+    end
+  end
+
+  describe '#branch_added?' do
+    context 'when old revision is defined' do
+      it { is_expected.not_to be_branch_added }
+    end
+
+    context 'when old revision is not defined' do
+      let(:oldrev) { Gitlab::Git::BLANK_SHA }
+
+      it { is_expected.to be_branch_added }
+    end
+  end
+
+  describe '#branch_removed?' do
+    context 'when new revision is defined' do
+      it { is_expected.not_to be_branch_removed }
+    end
+
+    context 'when new revision is not defined' do
+      let(:newrev) { Gitlab::Git::BLANK_SHA }
+
+      it { is_expected.to be_branch_removed }
+    end
+  end
+
+  describe '#modified_paths' do
+    context 'when a push is a branch update' do
+      let(:newrev) { '498214d' }
+      let(:oldrev) { '281d3a7' }
+
+      it 'returns modified paths' do
+        expect(subject.modified_paths).to eq ['bar/branch-test.txt',
+                                              'files/js/commit.coffee',
+                                              'with space/README.md']
+      end
+    end
+
+    context 'when a push is not a branch update' do
+      let(:oldrev) { Gitlab::Git::BLANK_SHA }
+
+      it 'raises an error' do
+        expect { subject.modified_paths }.to raise_error(ArgumentError)
+      end
+    end
+  end
+
+  describe '#oldrev' do
+    context 'when a valid oldrev is provided' do
+      it 'returns oldrev' do
+        expect(subject.oldrev).to eq oldrev
+      end
+    end
+
+    context 'when a nil valud is provided' do
+      let(:oldrev) { nil }
+
+      it 'returns blank SHA' do
+        expect(subject.oldrev).to eq Gitlab::Git::BLANK_SHA
+      end
+    end
+  end
+
+  describe '#newrev' do
+    context 'when valid newrev is provided' do
+      it 'returns newrev' do
+        expect(subject.newrev).to eq newrev
+      end
+    end
+
+    context 'when a nil valud is provided' do
+      let(:newrev) { nil }
+
+      it 'returns blank SHA' do
+        expect(subject.newrev).to eq Gitlab::Git::BLANK_SHA
+      end
+    end
+  end
+end

spec/models/ci/pipeline_spec.rb

@@ -825,6 +825,57 @@ describe Ci::Pipeline, :mailer do
     end
   end
 
+  describe '#branch_updated?' do
+    context 'when pipeline has before SHA' do
+      before do
+        pipeline.update_column(:before_sha, 'a1b2c3d4')
+      end
+
+      it 'runs on a branch update push' do
+        expect(pipeline.before_sha).not_to be Gitlab::Git::BLANK_SHA
+        expect(pipeline.branch_updated?).to be true
+      end
+    end
+
+    context 'when pipeline does not have before SHA' do
+      before do
+        pipeline.update_column(:before_sha, Gitlab::Git::BLANK_SHA)
+      end
+
+      it 'does not run on a branch updating push' do
+        expect(pipeline.branch_updated?).to be false
+      end
+    end
+  end
+
+  describe '#modified_paths' do
+    context 'when old and new revisions are set' do
+      let(:project) { create(:project, :repository) }
+
+      before do
+        pipeline.update(before_sha: '1234abcd', sha: '2345bcde')
+      end
+
+      it 'fetches stats for changes between commits' do
+        expect(project.repository)
+          .to receive(:diff_stats).with('1234abcd', '2345bcde')
+          .and_call_original
+
+        pipeline.modified_paths
+      end
+    end
+
+    context 'when either old or new revision is missing' do
+      before do
+        pipeline.update_column(:before_sha, Gitlab::Git::BLANK_SHA)
+      end
+
+      it 'raises an error' do
+        expect { pipeline.modified_paths }.to raise_error(ArgumentError)
+      end
+    end
+  end
+
   describe '#has_kubernetes_active?' do
     context 'when kubernetes is active' do
       shared_examples 'same behavior between KubernetesService and Platform::Kubernetes' do