Merge branch 'display-mr-link-if-thre-is-one' into 'master'

Replaces "Create merge request" link with one to the MR when one exists

Fixes #3716

* Without MR:

![before-1](/uploads/abcb2eb5bb5927a83c2f1700528f852c/before-1.png)

* With MR:

![after-1](/uploads/9020b871e1aa08d3e5a45359336ef0f2/after-1.png)

* Without MR:

![before-2](/uploads/bb3bd1a74efc193ad31af68f1e04ef5f/before-2.png)

* With MR:

![after-2](/uploads/789d32aef12f39c605e665d0c4bc9fbe/after-2.png)

* Without MR:

![before-3](/uploads/a9aff7a11eb1069be24c37a5455be809/before-3.png)

* With MR:

![after-3](/uploads/48fe81ea50657fe5b2de0d25260d8e4b/after-3.png)

See merge request !2670

5 files changed, 28 insertions, 9 deletions

diff --git a/app/controllers/projects/commits_controller.rb b/app/controllers/projects/commits_controller.rb
index bf5b54c8cb7..1420b96840c 100644
--- a/app/controllers/projects/commits_controller.rb
+++ b/app/controllers/projects/commits_controller.rb
@@ -21,6 +21,9 @@ class Projects::CommitsController < Projects::ApplicationController
     @note_counts = project.notes.where(commit_id: @commits.map(&:id)).
       group(:commit_id).count
 
+    @merge_request = @project.merge_requests.opened.
+      find_by(source_project: @project, source_branch: @ref, target_branch: @repository.root_ref)
+
     respond_to do |format|
       format.html
       format.json { pager_json("projects/commits/_commits", @commits.size) }
diff --git a/app/controllers/projects/compare_controller.rb b/app/controllers/projects/compare_controller.rb
index 7bbe75b3974..dc5d217f3e4 100644
--- a/app/controllers/projects/compare_controller.rb
+++ b/app/controllers/projects/compare_controller.rb
@@ -4,24 +4,23 @@ class Projects::CompareController < Projects::ApplicationController
   # Authorize
   before_action :require_non_empty_project
   before_action :authorize_download_code!
+  before_action :assign_ref_vars, only: [:index, :show]
+  before_action :merge_request, only: [:index, :show]
 
   def index
-    @ref = Addressable::URI.unescape(params[:to])
   end
 
   def show
-    base_ref = Addressable::URI.unescape(params[:from])
-    @ref = head_ref = Addressable::URI.unescape(params[:to])
     diff_options = { ignore_whitespace_change: true } if params[:w] == '1'
 
     compare_result = CompareService.new.
-      execute(@project, head_ref, @project, base_ref, diff_options)
+      execute(@project, @head_ref, @project, @base_ref, diff_options)
 
     if compare_result
       @commits = Commit.decorate(compare_result.commits, @project)
       @diffs = compare_result.diffs
-      @commit = @project.commit(head_ref)
-      @base_commit = @project.merge_base_commit(base_ref, head_ref)
+      @commit = @project.commit(@head_ref)
+      @base_commit = @project.merge_base_commit(@base_ref, @head_ref)
       @diff_refs = [@base_commit, @commit]
       @line_notes = []
     end
@@ -31,4 +30,16 @@ class Projects::CompareController < Projects::ApplicationController
     redirect_to namespace_project_compare_path(@project.namespace, @project,
                                                params[:from], params[:to])
   end
+
+  private
+
+  def assign_ref_vars
+    @base_ref = Addressable::URI.unescape(params[:from])
+    @ref = @head_ref = Addressable::URI.unescape(params[:to])
+  end
+
+  def merge_request
+    @merge_request ||= @project.merge_requests.opened.
+      find_by(source_project: @project, source_branch: @head_ref, target_branch: @base_ref)
+  end
 end
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index ddc476447ca..345b9a26d4e 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -137,6 +137,7 @@ class MergeRequest < ActiveRecord::Base
   scope :by_milestone, ->(milestone) { where(milestone_id: milestone) }
   scope :in_projects, ->(project_ids) { where("source_project_id in (:project_ids) OR target_project_id in (:project_ids)", project_ids: project_ids) }
   scope :of_projects, ->(ids) { where(target_project_id: ids) }
+  scope :opened, -> { with_state(:opened) }
   scope :merged, -> { with_state(:merged) }
   scope :closed, -> { with_state(:closed) }
   scope :closed_and_merged, -> { with_states(:closed, :merged) }
diff --git a/app/views/projects/commits/show.html.haml b/app/views/projects/commits/show.html.haml
index ede64d47ab3..c52cf25d40a 100644
--- a/app/views/projects/commits/show.html.haml
+++ b/app/views/projects/commits/show.html.haml
@@ -11,7 +11,10 @@
     = render 'shared/ref_switcher', destination: 'commits'
 
   .block-controls.hidden-xs.hidden-sm
-    - if create_mr_button?(@repository.root_ref, @ref)
+    - if @merge_request.present?
+      .control
+        = link_to "View Open Merge Request", namespace_project_merge_request_path(@project.namespace, @project, @merge_request), class: 'btn'
+    - elsif create_mr_button?(@repository.root_ref, @ref)
       .control
         = link_to create_mr_path(@repository.root_ref, @ref), class: 'btn btn-success' do
           = icon('plus')
diff --git a/app/views/projects/compare/_form.html.haml b/app/views/projects/compare/_form.html.haml
index efc25eda26b..4ab81f3635c 100644
--- a/app/views/projects/compare/_form.html.haml
+++ b/app/views/projects/compare/_form.html.haml
@@ -13,12 +13,13 @@
         = text_field_tag :to, params[:to], class: "form-control", required: true
     &nbsp;
     = button_tag "Compare", class: "btn btn-create commits-compare-btn"
-    - if create_mr_button?
+    - if @merge_request.present?
+      = link_to "View Open Merge Request", namespace_project_merge_request_path(@project.namespace, @project, @merge_request), class: 'prepend-left-10 btn'
+    - elsif create_mr_button?
       = link_to create_mr_path, class: 'prepend-left-10 btn' do
         = icon("plus")
         Create Merge Request
 
-
 :javascript
   var availableTags = #{@project.repository.ref_names.to_json};