Create merge request from email

* new merge request can be created by sending an email to the specific
email address (similar to creating issues by email)
* for the first iteration, source branch must be specified in the mail
subject, other merge request parameters can not be set yet
* user should enable "Receive notifications about your own activity" in
user settings to receive a notification about created merge request

Part of #32878

14 files changed, 67 insertions, 51 deletions

diff --git a/app/assets/javascripts/issuable_index.js b/app/assets/javascripts/issuable_index.js
index 0b123a11a3b..c3e0acdff66 100644
--- a/app/assets/javascripts/issuable_index.js
+++ b/app/assets/javascripts/issuable_index.js
@@ -28,7 +28,7 @@ export default class IssuableIndex {
         url: $('.incoming-email-token-reset').attr('href'),
         dataType: 'json',
         success(response) {
-          $('#issue_email').val(response.new_issue_address).focus();
+          $('#issuable_email').val(response.new_address).focus();
         },
         beforeSend() {
           $('.incoming-email-token-reset').text('resetting...');
diff --git a/app/assets/stylesheets/pages/issues.scss b/app/assets/stylesheets/pages/issues.scss
index d3dda2e7d25..8218326ae8f 100644
--- a/app/assets/stylesheets/pages/issues.scss
+++ b/app/assets/stylesheets/pages/issues.scss
@@ -164,12 +164,7 @@ ul.related-merge-requests > li {
   }
 }
 
-.issues-footer {
-  padding-top: $gl-padding;
-  padding-bottom: 37px;
-}
-
-.issue-email-modal-btn {
+.issuable-email-modal-btn {
   padding: 0;
   color: $gl-link-color;
   background-color: transparent;
diff --git a/app/assets/stylesheets/pages/projects.scss b/app/assets/stylesheets/pages/projects.scss
index 4c1e6d46242..9345177a4dc 100644
--- a/app/assets/stylesheets/pages/projects.scss
+++ b/app/assets/stylesheets/pages/projects.scss
@@ -1210,3 +1210,8 @@ pre.light-well {
     border-color: $border-color;
   }
 }
+
+.issuable-footer {
+  padding-top: $gl-padding;
+  padding-bottom: 37px;
+}
diff --git a/app/controllers/projects_controller.rb b/app/controllers/projects_controller.rb
index a784c6f402a..3882fa4791d 100644
--- a/app/controllers/projects_controller.rb
+++ b/app/controllers/projects_controller.rb
@@ -133,11 +133,11 @@ class ProjectsController < Projects::ApplicationController
     redirect_to edit_project_path(@project), status: 302, alert: ex.message
   end
 
-  def new_issue_address
+  def new_issuable_address
     return render_404 unless Gitlab::IncomingEmail.supports_issue_creation?
 
     current_user.reset_incoming_email_token!
-    render json: { new_issue_address: @project.new_issue_address(current_user) }
+    render json: { new_address: @project.new_issuable_address(current_user, params[:issuable_type]) }
   end
 
   def archive
diff --git a/app/models/project.rb b/app/models/project.rb
index 0a7e7617d9b..cc530076bf7 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -752,13 +752,14 @@ class Project < ActiveRecord::Base
     Gitlab::Routing.url_helpers.project_url(self)
   end
 
-  def new_issue_address(author)
+  def new_issuable_address(author, address_type)
     return unless Gitlab::IncomingEmail.supports_issue_creation? && author
 
     author.ensure_incoming_email_token!
 
+    suffix = address_type == 'merge_request' ? '+merge-request' : ''
     Gitlab::IncomingEmail.reply_address(
-      "#{full_path}+#{author.incoming_email_token}")
+      "#{full_path}#{suffix}+#{author.incoming_email_token}")
   end
 
   def build_commit_note(commit)
diff --git a/app/services/merge_requests/build_service.rb b/app/services/merge_requests/build_service.rb
index c2fb01466df..9622a5c5462 100644
--- a/app/services/merge_requests/build_service.rb
+++ b/app/services/merge_requests/build_service.rb
@@ -10,8 +10,12 @@ module MergeRequests
       merge_request.target_branch   = find_target_branch
       merge_request.can_be_created  = branches_valid?
 
-      compare_branches if branches_present?
-      assign_title_and_description if merge_request.can_be_created
+      # compare branches only if branches are valid, otherwise
+      # compare_branches may raise an error
+      if merge_request.can_be_created
+        compare_branches
+        assign_title_and_description
+      end
 
       merge_request
     end
diff --git a/app/services/merge_requests/create_service.rb b/app/services/merge_requests/create_service.rb
index 820709583fa..49cf534dc0d 100644
--- a/app/services/merge_requests/create_service.rb
+++ b/app/services/merge_requests/create_service.rb
@@ -35,6 +35,12 @@ module MergeRequests
       super
     end
 
+    # expose issuable create method so it can be called from email
+    # handler CreateMergeRequestHandler
+    def create(merge_request)
+      super
+    end
+
     private
 
     def update_merge_requests_head_pipeline(merge_request)
diff --git a/app/views/projects/_issuable_by_email.html.haml b/app/views/projects/_issuable_by_email.html.haml
new file mode 100644
index 00000000000..749e273b2e2
--- /dev/null
+++ b/app/views/projects/_issuable_by_email.html.haml
@@ -0,0 +1,30 @@
+- name = issuable_type == 'issue' ? 'issue' : 'merge request'
+
+.issuable-footer.text-center
+  %button.issuable-email-modal-btn{ type: "button", data: { toggle: "modal", target: "#issuable-email-modal" } }
+    Email a new #{name} to this project
+
+#issuable-email-modal.modal.fade{ tabindex: "-1", role: "dialog" }
+  .modal-dialog{ role: "document" }
+    .modal-content
+      .modal-header
+        %button.close{ type: "button", data: { dismiss: "modal" }, aria: { label: "close" } }
+          %span{ aria: { hidden: "true" } }= icon("times")
+        %h4.modal-title
+          Create new #{name} by email
+      .modal-body
+        %p
+          You can create a new #{name} inside this project by sending an email to the following email address:
+        .email-modal-input-group.input-group
+          = text_field_tag :issuable_email, email, class: "monospace js-select-on-focus form-control", readonly: true
+          .input-group-btn
+            = clipboard_button(target: '#issuable_email')
+        %p
+          = render 'by_email_description'
+        %p
+          This is a private email address, generated just for you.
+
+          Anyone who gets ahold of it can create issues or merge requests as if they were you.
+          You should
+          = link_to 'reset it', new_issuable_address_project_path(@project, issuable_type: issuable_type), class: 'incoming-email-token-reset'
+          if that ever happens.
diff --git a/app/views/projects/issues/_by_email_description.html.haml b/app/views/projects/issues/_by_email_description.html.haml
new file mode 100644
index 00000000000..f2d58534903
--- /dev/null
+++ b/app/views/projects/issues/_by_email_description.html.haml
@@ -0,0 +1,6 @@
+The subject will be used as the title of the new issue, and the message will be the description.
+
+= link_to 'Quick actions', help_page_path('user/project/quick_actions'), target: '_blank', tabindex: -1
+and styling with
+= link_to 'Markdown', help_page_path('user/markdown'), target: '_blank', tabindex: -1
+are supported.
diff --git a/app/views/projects/issues/_issue_by_email.html.haml b/app/views/projects/issues/_issue_by_email.html.haml
deleted file mode 100644
index 264032a3a31..00000000000
--- a/app/views/projects/issues/_issue_by_email.html.haml
+++ /dev/null
@@ -1,34 +0,0 @@
-.issues-footer.text-center
-  %button.issue-email-modal-btn{ type: "button", data: { toggle: "modal", target: "#issue-email-modal" } }
-    Email a new issue to this project
-
-#issue-email-modal.modal.fade{ tabindex: "-1", role: "dialog" }
-  .modal-dialog{ role: "document" }
-    .modal-content
-      .modal-header
-        %button.close{ type: "button", data: { dismiss: "modal" }, aria: { label: "close" } }
-          %span{ aria: { hidden: "true" } }= icon("times")
-        %h4.modal-title
-          Create new issue by email
-      .modal-body
-        %p
-          You can create a new issue inside this project by sending an email to the following email address:
-        .email-modal-input-group.input-group
-          = text_field_tag :issue_email, email, class: "monospace js-select-on-focus form-control", readonly: true
-          .input-group-btn
-            = clipboard_button(target: '#issue_email')
-        %p
-          The subject will be used as the title of the new issue, and the message will be the description.
-
-          = link_to 'Quick actions', help_page_path('user/project/quick_actions'), target: '_blank', tabindex: -1
-          and styling with
-          = link_to 'Markdown', help_page_path('user/markdown'), target: '_blank', tabindex: -1
-          are supported.
-
-        %p
-          This is a private email address, generated just for you.
-
-          Anyone who gets ahold of it can create issues as if they were you.
-          You should
-          = link_to 'reset it', new_issue_address_project_path(@project), class: 'incoming-email-token-reset'
-          if that ever happens.
diff --git a/app/views/projects/issues/index.html.haml b/app/views/projects/issues/index.html.haml
index bfaf024428d..193111b4cee 100644
--- a/app/views/projects/issues/index.html.haml
+++ b/app/views/projects/issues/index.html.haml
@@ -2,7 +2,7 @@
 - @can_bulk_update = can?(current_user, :admin_issue, @project)
 
 - page_title "Issues"
-- new_issue_email = @project.new_issue_address(current_user)
+- new_issue_email = @project.new_issuable_address(current_user, 'issue')
 
 - content_for :page_specific_javascripts do
   = webpack_bundle_tag 'common_vue'
@@ -25,6 +25,6 @@
     .issues-holder
       = render 'issues'
       - if new_issue_email
-        = render 'issue_by_email', email: new_issue_email
+        = render 'projects/issuable_by_email', email: new_issue_email, issuable_type: 'issue'
 - else
   = render 'shared/empty_states/issues', button_path: new_project_issue_path(@project)
diff --git a/app/views/projects/merge_requests/_by_email_description.html.haml b/app/views/projects/merge_requests/_by_email_description.html.haml
new file mode 100644
index 00000000000..8ba251749b8
--- /dev/null
+++ b/app/views/projects/merge_requests/_by_email_description.html.haml
@@ -0,0 +1 @@
+The subject will be used as the source branch name for the new merge request and the target branch will be the default branch for the project.
diff --git a/app/views/projects/merge_requests/index.html.haml b/app/views/projects/merge_requests/index.html.haml
index 8da2243adef..2ded7484151 100644
--- a/app/views/projects/merge_requests/index.html.haml
+++ b/app/views/projects/merge_requests/index.html.haml
@@ -4,6 +4,7 @@
 - new_merge_request_path = project_new_merge_request_path(merge_project) if merge_project
 
 - page_title "Merge Requests"
+- new_merge_request_email = @project.new_issuable_address(current_user, 'merge_request')
 
 - content_for :page_specific_javascripts do
   = webpack_bundle_tag 'common_vue'
@@ -25,5 +26,7 @@
 
     .merge-requests-holder
       = render 'merge_requests'
+      - if new_merge_request_email
+        = render 'projects/issuable_by_email', email: new_merge_request_email, issuable_type: 'merge_request'
 - else
   = render 'shared/empty_states/merge_requests', button_path: new_merge_request_path
diff --git a/app/workers/email_receiver_worker.rb b/app/workers/email_receiver_worker.rb
index 1afa24c8e2a..05cb116a623 100644
--- a/app/workers/email_receiver_worker.rb
+++ b/app/workers/email_receiver_worker.rb
@@ -39,8 +39,7 @@ class EmailReceiverWorker
         "You are not allowed to perform this action. If you believe this is in error, contact a staff member."
       when Gitlab::Email::NoteableNotFoundError
         "The thread you are replying to no longer exists, perhaps it was deleted? If you believe this is in error, contact a staff member."
-      when Gitlab::Email::InvalidNoteError,
-           Gitlab::Email::InvalidIssueError
+      when Gitlab::Email::InvalidRecordError
         can_retry = true
         e.message
       end