diff --git a/.rubocop_todo/layout/line_length.yml b/.rubocop_todo/layout/line_length.yml
index 78c086d2a08f0736b2dab4589ea78da7591f466d..7fa37562b46bdc019b842e2193914ac03fce4547 100644
--- a/.rubocop_todo/layout/line_length.yml
+++ b/.rubocop_todo/layout/line_length.yml
@@ -3270,7 +3270,6 @@ Layout/LineLength:
     - 'lib/gitlab/lograge/custom_options.rb'
     - 'lib/gitlab/mail_room/authenticator.rb'
     - 'lib/gitlab/markdown_cache/active_record/extension.rb'
-    - 'lib/gitlab/merge_requests/commit_message_generator.rb'
     - 'lib/gitlab/metrics/dashboard/importer.rb'
     - 'lib/gitlab/metrics/dashboard/importers/prometheus_metrics.rb'
     - 'lib/gitlab/metrics/dashboard/stages/cluster_endpoint_inserter.rb'
@@ -4606,7 +4605,6 @@ Layout/LineLength:
     - 'spec/lib/gitlab/legacy_github_import/pull_request_formatter_spec.rb'
     - 'spec/lib/gitlab/lfs/client_spec.rb'
     - 'spec/lib/gitlab/mail_room/authenticator_spec.rb'
-    - 'spec/lib/gitlab/merge_requests/commit_message_generator_spec.rb'
     - 'spec/lib/gitlab/metrics/background_transaction_spec.rb'
     - 'spec/lib/gitlab/metrics/boot_time_tracker_spec.rb'
     - 'spec/lib/gitlab/metrics/dashboard/finder_spec.rb'
diff --git a/.rubocop_todo/layout/space_in_lambda_literal.yml b/.rubocop_todo/layout/space_in_lambda_literal.yml
index 6bb31295fbd9da3a42be39ef3bfcf9be900688e9..31b73fbe8a3a2552a8489dd0d09672c7824bb634 100644
--- a/.rubocop_todo/layout/space_in_lambda_literal.yml
+++ b/.rubocop_todo/layout/space_in_lambda_literal.yml
@@ -396,7 +396,6 @@ Layout/SpaceInLambdaLiteral:
     - 'lib/gitlab/gl_repository.rb'
     - 'lib/gitlab/health_checks/server.rb'
     - 'lib/gitlab/import_export/import_failure_service.rb'
-    - 'lib/gitlab/merge_requests/commit_message_generator.rb'
     - 'lib/gitlab/metrics/dashboard/transformers/yml/v1/prometheus_metrics.rb'
     - 'lib/gitlab/metrics/exporter/base_exporter.rb'
     - 'lib/gitlab/visibility_level.rb'
diff --git a/.rubocop_todo/rails/pluck.yml b/.rubocop_todo/rails/pluck.yml
index 6aeca1b7ea8b35c6be52e619c2af010a544d5f41..e094a3397a6fc50eca0f5008229421f719722387 100644
--- a/.rubocop_todo/rails/pluck.yml
+++ b/.rubocop_todo/rails/pluck.yml
@@ -126,7 +126,7 @@ Rails/Pluck:
     - 'lib/gitlab/git_access.rb'
     - 'lib/gitlab/github_import/representation/issue.rb'
     - 'lib/gitlab/jira_import/metadata_collector.rb'
-    - 'lib/gitlab/merge_requests/commit_message_generator.rb'
+    - 'lib/gitlab/merge_requests/message_generator.rb'
     - 'lib/gitlab/metrics/dashboard/importers/prometheus_metrics.rb'
     - 'lib/gitlab/metrics/dashboard/stages/custom_metrics_details_inserter.rb'
     - 'lib/gitlab/sidekiq_config/cli_methods.rb'
diff --git a/.rubocop_todo/rspec/context_wording.yml b/.rubocop_todo/rspec/context_wording.yml
index 523cc1bfad9d4fbb9b93571254b6d44751445059..7131626d15b51b1425b91ca5192abeac26943e00 100644
--- a/.rubocop_todo/rspec/context_wording.yml
+++ b/.rubocop_todo/rspec/context_wording.yml
@@ -2023,7 +2023,7 @@ RSpec/ContextWording:
     - 'spec/lib/gitlab/markdown_cache/active_record/extension_spec.rb'
     - 'spec/lib/gitlab/memory/reports_daemon_spec.rb'
     - 'spec/lib/gitlab/memory/watchdog_spec.rb'
-    - 'spec/lib/gitlab/merge_requests/commit_message_generator_spec.rb'
+    - 'spec/lib/gitlab/merge_requests/message_generator_spec.rb'
     - 'spec/lib/gitlab/metrics/dashboard/cache_spec.rb'
     - 'spec/lib/gitlab/metrics/dashboard/importer_spec.rb'
     - 'spec/lib/gitlab/metrics/dashboard/importers/prometheus_metrics_spec.rb'
diff --git a/.rubocop_todo/rspec/verified_doubles.yml b/.rubocop_todo/rspec/verified_doubles.yml
index 1d4b6d23e0d65d2ae57e0910550301d3f2385158..8fa03c775be607c6457945439aa8e88fb80061dd 100644
--- a/.rubocop_todo/rspec/verified_doubles.yml
+++ b/.rubocop_todo/rspec/verified_doubles.yml
@@ -633,7 +633,7 @@ RSpec/VerifiedDoubles:
     - 'spec/lib/gitlab/mail_room/mail_room_spec.rb'
     - 'spec/lib/gitlab/manifest_import/metadata_spec.rb'
     - 'spec/lib/gitlab/markdown_cache/field_data_spec.rb'
-    - 'spec/lib/gitlab/merge_requests/commit_message_generator_spec.rb'
+    - 'spec/lib/gitlab/merge_requests/message_generator_spec.rb'
     - 'spec/lib/gitlab/merge_requests/mergeability/redis_interface_spec.rb'
     - 'spec/lib/gitlab/metrics/boot_time_tracker_spec.rb'
     - 'spec/lib/gitlab/metrics/dashboard/importers/prometheus_metrics_spec.rb'
diff --git a/.rubocop_todo/style/accessor_grouping.yml b/.rubocop_todo/style/accessor_grouping.yml
index 27b14007afde179c4752b504265bf9004c86ac4b..a558681388544143ac1d97c67a980e20947293a8 100644
--- a/.rubocop_todo/style/accessor_grouping.yml
+++ b/.rubocop_todo/style/accessor_grouping.yml
@@ -57,7 +57,6 @@ Style/AccessorGrouping:
     - 'lib/gitlab/http_io.rb'
     - 'lib/gitlab/import_export/group/legacy_tree_restorer.rb'
     - 'lib/gitlab/import_export/project/tree_restorer.rb'
-    - 'lib/gitlab/merge_requests/commit_message_generator.rb'
     - 'lib/gitlab/sidekiq_daemon/monitor.rb'
     - 'lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job.rb'
     - 'lib/gitlab/suggestions/file_suggestion.rb'
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 9b7c14c6a0e22fd9eef3aea497174fa0e19f3b97..f9d1185498197caa59d097721442863eb0b434d8 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -1383,7 +1383,7 @@ def target_branch_exists?
 
   def default_merge_commit_message(include_description: false, user: nil)
     if self.target_project.merge_commit_template.present? && !include_description
-      return ::Gitlab::MergeRequests::CommitMessageGenerator.new(merge_request: self, current_user: user).merge_message
+      return ::Gitlab::MergeRequests::MessageGenerator.new(merge_request: self, current_user: user).merge_commit_message
     end
 
     closes_issues_references = visible_closing_issues_for.map do |issue|
@@ -1407,7 +1407,7 @@ def default_merge_commit_message(include_description: false, user: nil)
 
   def default_squash_commit_message(user: nil)
     if self.target_project.squash_commit_template.present?
-      return ::Gitlab::MergeRequests::CommitMessageGenerator.new(merge_request: self, current_user: user).squash_message
+      return ::Gitlab::MergeRequests::MessageGenerator.new(merge_request: self, current_user: user).squash_commit_message
     end
 
     title
diff --git a/app/services/merge_requests/build_service.rb b/app/services/merge_requests/build_service.rb
index cc786ac02bd601837f889d10f7a567341119861b..b9a681f29dbb6de17391a00eccaa1c95daba4810 100644
--- a/app/services/merge_requests/build_service.rb
+++ b/app/services/merge_requests/build_service.rb
@@ -224,6 +224,7 @@ def set_draft_title_if_needed
     #
     def assign_title_and_description
       assign_description_from_repository_template
+      replace_variables_in_description
       assign_title_and_description_from_commits
       merge_request.title ||= title_from_issue if target_project.issues_enabled? || target_project.external_issue_tracker
       merge_request.title ||= source_branch.titleize.humanize
@@ -318,6 +319,15 @@ def assign_description_from_repository_template
       merge_request.description = repository_template.content
     end
 
+    def replace_variables_in_description
+      return unless merge_request.description.present?
+
+      merge_request.description = ::Gitlab::MergeRequests::MessageGenerator.new(
+        merge_request: merge_request,
+        current_user: current_user
+      ).new_mr_description
+    end
+
     def issue_iid
       strong_memoize(:issue_iid) do
         @params_issue_iid || begin
diff --git a/doc/user/project/description_templates.md b/doc/user/project/description_templates.md
index 40c36236932ff5b06c7ec846c9234ec1bc2fc0ff..7774b567e8b529eceda1a788f6fea1a14dd12625 100644
--- a/doc/user/project/description_templates.md
+++ b/doc/user/project/description_templates.md
@@ -83,6 +83,22 @@ NOTE:
 You can create shortcut links to create an issue using a designated template.
 For example: `https://gitlab.com/gitlab-org/gitlab/-/issues/new?issuable_template=Feature%20proposal`. Read more about [creating issues using a URL with prefilled values](issues/managing_issues.md#using-a-url-with-prefilled-values).
 
+### Supported variables in merge request templates
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/89810) in GitLab 15.7.
+
+When you save a merge request for the first time, GitLab replaces these variables in
+your merge request template with their values:
+
+| Variable | Description | Output example |
+|----------|-------------|----------------|
+| `%{all_commits}` | Messages from all commits in the merge request. Limited to 100 most recent commits. Skips commit bodies exceeding 100 KiB and merge commit messages. | `* Feature introduced` <br><br> `This commit implements feature` <br> `Changelog:added` <br><br> `* Bug fixed` <br><br> `* Documentation improved` <br><br>`This commit introduced better docs.` |
+| `%{co_authored_by}` | Names and emails of commit authors in a `Co-authored-by` Git commit trailer format. Limited to authors of 100 most recent commits in merge request. | `Co-authored-by: Zane Doe <zdoe@example.com>` <br> `Co-authored-by: Blake Smith <bsmith@example.com>` |
+| `%{first_commit}` | Full message of the first commit in merge request diff. | `Update README.md` |
+| `%{first_multiline_commit}` | Full message of the first commit that's not a merge commit and has more than one line in message body. Merge request title if all commits aren't multiline. | `Update README.md`<br><br>`Improved project description in readme file.` |
+| `%{source_branch}` | The name of the branch being merged. | `my-feature-branch`  |
+| `%{target_branch}` | The name of the branch that the changes are applied to. | `main` |
+
 ### Set instance-level description templates **(PREMIUM SELF)**
 
 You can set a description template at the **instance level** for issues
diff --git a/lib/gitlab/merge_requests/commit_message_generator.rb b/lib/gitlab/merge_requests/message_generator.rb
similarity index 58%
rename from lib/gitlab/merge_requests/commit_message_generator.rb
rename to lib/gitlab/merge_requests/message_generator.rb
index b09e2150012dc833e6956c285bc8481149a41026..5113fbdcd7b0229c210e26337c515efb96a68ad6 100644
--- a/lib/gitlab/merge_requests/commit_message_generator.rb
+++ b/lib/gitlab/merge_requests/message_generator.rb
@@ -1,28 +1,41 @@
 # frozen_string_literal: true
 module Gitlab
   module MergeRequests
-    class CommitMessageGenerator
+    class MessageGenerator
       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
+      def merge_commit_message
         return unless @merge_request.target_project.merge_commit_template.present?
 
-        replace_placeholders(@merge_request.target_project.merge_commit_template)
+        replace_placeholders(@merge_request.target_project.merge_commit_template, allowed_placeholders: PLACEHOLDERS)
       end
 
-      def squash_message
+      def squash_commit_message
         return unless @merge_request.target_project.squash_commit_template.present?
 
-        replace_placeholders(@merge_request.target_project.squash_commit_template, squash: true)
+        replace_placeholders(
+          @merge_request.target_project.squash_commit_template,
+          allowed_placeholders: PLACEHOLDERS,
+          squash: true
+        )
+      end
+
+      def new_mr_description
+        return unless @merge_request.description.present?
+
+        replace_placeholders(
+          @merge_request.description,
+          allowed_placeholders: ALLOWED_NEW_MR_PLACEHOLDERS,
+          keep_carriage_return: true
+        )
       end
 
       private
 
-      attr_reader :merge_request
-      attr_reader :current_user
+      attr_reader :merge_request, :current_user
 
       PLACEHOLDERS = {
         'source_branch' => ->(merge_request, _, _) { merge_request.source_branch.to_s },
@@ -38,11 +51,25 @@ def squash_message
         end,
         '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 },
+        'first_commit' => -> (merge_request, _, _) {
+          return unless merge_request.persisted? || merge_request.compare_commits.present?
+
+          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) },
-        'reviewed_by' => ->(merge_request, _, _) { merge_request.reviewed_by_users.map { |user| "Reviewed-by: #{user.name} <#{user.commit_email_or_default}>" }.join("\n") },
-        'approved_by' => ->(merge_request, _, _) { merge_request.approved_by_users.map { |user| "Approved-by: #{user.name} <#{user.commit_email_or_default}>" }.join("\n") },
+        'reviewed_by' => ->(merge_request, _, _) {
+          merge_request.reviewed_by_users
+                       .map { |user| "Reviewed-by: #{user.name} <#{user.commit_email_or_default}>" }
+                       .join("\n")
+        },
+        '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
@@ -67,15 +94,34 @@ def squash_message
         end
       }.freeze
 
+      # A new merge request that is in the process of being created and hasn't
+      # been persisted to the database.
+      #
+      # Limit the placeholders to a subset of the available ones where the
+      # placeholders wouldn't make sense in context. Disallowed placeholders
+      # will be replaced with an empty string.
+      ALLOWED_NEW_MR_PLACEHOLDERS = %w[
+        source_branch
+        target_branch
+        first_commit
+        first_multiline_commit
+        co_authored_by
+        all_commits
+      ].freeze
+
       PLACEHOLDERS_COMBINED_REGEX = /%{(#{Regexp.union(PLACEHOLDERS.keys)})}/.freeze
 
-      def replace_placeholders(message, squash: false)
+      def replace_placeholders(message, allowed_placeholders: [], squash: false, keep_carriage_return: false)
         # Convert CRLF to LF.
-        message = message.delete("\r")
+        message = message.delete("\r") unless keep_carriage_return
 
         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)]
+          replacement = if allowed_placeholders.include?(variable_name)
+                          PLACEHOLDERS[variable_name].call(merge_request, current_user, squash)
+                        end
+
+          ["%{#{variable_name}}", replacement]
         end
         names_of_empty_variables = values.filter_map { |name, value| name if value.blank? }
 
diff --git a/spec/lib/gitlab/merge_requests/commit_message_generator_spec.rb b/spec/lib/gitlab/merge_requests/message_generator_spec.rb
similarity index 87%
rename from spec/lib/gitlab/merge_requests/commit_message_generator_spec.rb
rename to spec/lib/gitlab/merge_requests/message_generator_spec.rb
index bdc9879f36298cd85379635886a1db9c7dfa664e..fbdd6a1e56d58eae31151096d0f4597d44a8d8fa 100644
--- a/spec/lib/gitlab/merge_requests/commit_message_generator_spec.rb
+++ b/spec/lib/gitlab/merge_requests/message_generator_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe Gitlab::MergeRequests::CommitMessageGenerator do
+RSpec.describe Gitlab::MergeRequests::MessageGenerator do
   let(:merge_commit_template) { nil }
   let(:squash_commit_template) { nil }
   let(:project) do
@@ -59,7 +59,14 @@
 
     context 'when project has commit template with only the title' do
       let(:merge_request) do
-        double(:merge_request, title: 'Fixes', target_project: project, to_reference: '!123', metrics: nil, merge_user: nil)
+        double(
+          :merge_request,
+          title: 'Fixes',
+          target_project: project,
+          to_reference: '!123',
+          metrics: nil,
+          merge_user: nil
+        )
       end
 
       let(message_template_name) { '%{title}' }
@@ -214,7 +221,7 @@
 
     context 'when project has template with CRLF newlines' do
       let(message_template_name) do
-        "Merge branch '%{source_branch}' into '%{target_branch}'\r\n\r\n%{title}\r\n\r\n%{description}\r\n\r\nSee merge request %{reference}"
+        "Merge branch '%{source_branch}' into '%{target_branch}'\r\n\r\n%{title}\r\n\r\n%{description}\r\n\r\nSee merge request %{reference}" # rubocop: disable Layout/LineLength
       end
 
       it 'converts it to LF newlines' do
@@ -717,8 +724,8 @@
     end
   end
 
-  describe '#merge_message' do
-    let(:result_message) { subject.merge_message }
+  describe '#merge_commit_message' do
+    let(:result_message) { subject.merge_commit_message }
 
     it_behaves_like 'commit message with template', :merge_commit_template
 
@@ -749,8 +756,8 @@
     end
   end
 
-  describe '#squash_message' do
-    let(:result_message) { subject.squash_message }
+  describe '#squash_commit_message' do
+    let(:result_message) { subject.squash_commit_message }
 
     it_behaves_like 'commit message with template', :squash_commit_template
 
@@ -780,4 +787,95 @@
       end
     end
   end
+
+  describe '#new_mr_description' do
+    let(:merge_request) do
+      build(
+        :merge_request,
+        source_project: project,
+        target_project: project,
+        target_branch: 'master',
+        source_branch: source_branch,
+        author: author,
+        description: merge_request_description,
+        title: merge_request_title
+      )
+    end
+
+    let(:result_message) { subject.new_mr_description }
+
+    before do
+      compare = CompareService.new(
+        project,
+        merge_request.source_branch
+      ).execute(
+        project,
+        merge_request.target_branch
+      )
+
+      merge_request.compare_commits = compare.commits
+      merge_request.compare = compare
+    end
+
+    context 'when project has template with all variables' do
+      let(:merge_request_description) { <<~MSG.rstrip }
+        source_branch:%{source_branch}
+        target_branch:%{target_branch}
+        title:%{title}
+        issues:%{issues}
+        description:%{description}
+        first_commit:%{first_commit}
+        first_multiline_commit:%{first_multiline_commit}
+        url:%{url}
+        approved_by:%{approved_by}
+        merged_by:%{merged_by}
+        co_authored_by:%{co_authored_by}
+        all_commits:%{all_commits}
+      MSG
+
+      it 'renders only variables specific to a new non-persisted merge request' do
+        expect(result_message).to eq <<~MSG.rstrip
+          source_branch:feature
+          target_branch:master
+          title:
+          issues:
+          description:
+          first_commit:Feature added
+
+          Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
+          first_multiline_commit:Feature added
+
+          Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
+          url:
+          approved_by:
+          merged_by:
+          co_authored_by:Co-authored-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
+          all_commits:* Feature added
+
+          Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
+        MSG
+      end
+
+      context 'when no first commit exists' do
+        let(:source_branch) { 'master' }
+
+        it 'does not populate any commit-related variables' do
+          expect(result_message).to eq <<~MSG.rstrip
+            source_branch:master
+            target_branch:master
+            title:
+            issues:
+            description:
+            first_commit:
+            first_multiline_commit:Bugfix
+            url:
+            approved_by:
+            merged_by:
+            co_authored_by:
+            all_commits:
+          MSG
+        end
+      end
+    end
+  end
 end
diff --git a/spec/services/merge_requests/build_service_spec.rb b/spec/services/merge_requests/build_service_spec.rb
index 4f27ff30da717fc4979d9e082f22bf7673784f01..79c779678a45efc23088a6c4e678f1e16b72b8e9 100644
--- a/spec/services/merge_requests/build_service_spec.rb
+++ b/spec/services/merge_requests/build_service_spec.rb
@@ -25,7 +25,9 @@
       safe_message: 'Initial commit',
       gitaly_commit?: false,
       id: 'f00ba6',
-      parent_ids: ['f00ba5'])
+      parent_ids: ['f00ba5'],
+      author_email: 'tom@example.com',
+      author_name: 'Tom Example')
   end
 
   let(:commit_2) do
@@ -34,7 +36,9 @@
       safe_message: "Closes #1234 Second commit\n\nCreate the app",
       gitaly_commit?: false,
       id: 'f00ba7',
-      parent_ids: ['f00ba6'])
+      parent_ids: ['f00ba6'],
+      author_email: 'alice@example.com',
+      author_name: 'Alice Example')
   end
 
   let(:commit_3) do
@@ -43,7 +47,9 @@
       safe_message: 'This is a bad commit message!',
       gitaly_commit?: false,
       id: 'f00ba8',
-      parent_ids: ['f00ba7'])
+      parent_ids: ['f00ba7'],
+      author_email: 'jo@example.com',
+      author_name: 'Jo Example')
   end
 
   let(:commits) { nil }
@@ -742,4 +748,91 @@ def stub_compare
       end
     end
   end
+
+  describe '#replace_variables_in_description' do
+    context 'when the merge request description is blank' do
+      let(:description) { nil }
+
+      it 'does not update the description' do
+        expect(merge_request.description).to eq(nil)
+      end
+    end
+
+    context 'when the merge request description contains template variables' do
+      let(:description) { <<~MSG.rstrip }
+        source_branch:%{source_branch}
+        target_branch:%{target_branch}
+        title:%{title}
+        issues:%{issues}
+        description:%{description}
+        first_commit:%{first_commit}
+        first_multiline_commit:%{first_multiline_commit}
+        url:%{url}
+        approved_by:%{approved_by}
+        merged_by:%{merged_by}
+        co_authored_by:%{co_authored_by}
+        all_commits:%{all_commits}
+      MSG
+
+      context 'when there are multiple commits in the diff' do
+        let(:commits) { Commit.decorate([commit_1, commit_2, commit_3], project) }
+
+        before do
+          stub_compare
+        end
+
+        it 'replaces the variables in the description' do
+          expect(merge_request.description).to eq <<~MSG.rstrip
+            source_branch:feature-branch
+            target_branch:master
+            title:
+            issues:
+            description:
+            first_commit:Initial commit
+            first_multiline_commit:Closes #1234 Second commit
+
+            Create the app
+            url:
+            approved_by:
+            merged_by:
+            co_authored_by:Co-authored-by: Jo Example <jo@example.com>
+            Co-authored-by: Alice Example <alice@example.com>
+            Co-authored-by: Tom Example <tom@example.com>
+            all_commits:* This is a bad commit message!
+
+            * Closes #1234 Second commit
+
+            Create the app
+
+            * Initial commit
+          MSG
+        end
+      end
+
+      context 'when there are no commits in the diff' do
+        let(:commits) { [] }
+
+        before do
+          stub_compare
+        end
+
+        it 'replaces the variables in the description' do
+          expect(merge_request.description).to eq <<~MSG.rstrip
+            source_branch:feature-branch
+            target_branch:master
+            title:
+            issues:
+            description:
+            first_commit:
+            first_multiline_commit:
+            url:
+            approved_by:
+            merged_by:
+            co_authored_by:
+            all_commits:
+          MSG
+        end
+      end
+    end
+  end
 end