Merge branch 'edit-on-fork' into 'master'

Automatically fork a project when not allowed to edit a file.

Fixes #3215.

To do:

- [ ] Add tests

-----

## "Edit" button on file in a project the user does NOT have write access to

![edit_file](/uploads/7602157420768aef483a6586bba2d164/edit_file.png)

## Clicking will automatically create a fork

![during_fork](/uploads/32f4f5dff9f24ea99522000b0bf881c5/during_fork.png)

## When the fork has been created, the user is returned to the edit page on the original project with a notice

![edit_notice](/uploads/94ed1319404370ff1e9c0d672fb41e03/edit_notice.png)

## The user cannot change the target branch and is informed that editing will start an MR

![edit_footer](/uploads/4da68d4795c7177e575b7c434d16eeae/edit_footer.png)

## Hitting "Commit changes" will commit and start an MR from my fork to the origin project

![Screen_Shot_2015-12-17_at_23.38.08](/uploads/d777a4db6f38a5a1be84031694465bc1/Screen_Shot_2015-12-17_at_23.38.08.png)

-----

## "Create file, "Upload file" and "New directory" buttons in a project the user does NOT have write access to

![new_directory](/uploads/72f556248f30d6652523bbb4be01b3e0/new_directory.png)

## Clicking any of these options will automatically create a fork

![during_fork](/uploads/32f4f5dff9f24ea99522000b0bf881c5/during_fork.png)

## When the fork has been created, the user is returned to the tree page on the original project with a notice

![new_directory_notice](/uploads/a1a3e11308ae0e8f0913fae6813a37ed/new_directory_notice.png)

## Clicking "New directory" again will show the modal. The user cannot change the target branch and is informed that editing will start an MR

![new_dir](/uploads/99ca8cbfb2f70603e352b3fdf67b6281/new_dir.png)

## Hitting "Create directory" will commit and start an MR from my fork to the origin project

![Screen_Shot_2015-12-17_at_23.39.19](/uploads/3713d0235abf831361b803a6198c5bc1/Screen_Shot_2015-12-17_at_23.39.19.png)

cc @dzaporozhets @skyruler

See merge request !2145

2 files changed, 113 insertions, 30 deletions

diff --git a/app/helpers/blob_helper.rb b/app/helpers/blob_helper.rb
index 68e5d5be600..d31d4cde08f 100644
--- a/app/helpers/blob_helper.rb
+++ b/app/helpers/blob_helper.rb
@@ -22,32 +22,90 @@ module BlobHelper
     %w(credits changelog news copying copyright license authors)
   end
 
-  def edit_blob_link(project, ref, path, options = {})
-    blob =
-      begin
-        project.repository.blob_at(ref, path)
-      rescue
-        nil
-      end
-
-    return unless blob && blob.text? && blob_editable?(blob)
-
-    text = 'Edit'
-    after = options[:after] || ''
+  def edit_blob_link(project = @project, ref = @ref, path = @path, options = {})
+    return unless current_user
+
+    blob = project.repository.blob_at(ref, path) rescue nil
+
+    return unless blob && blob_text_viewable?(blob)
+
     from_mr = options[:from_merge_request_id]
     link_opts = {}
     link_opts[:from_merge_request_id] = from_mr if from_mr
-    cls = 'btn btn-small'
-    link_to(text,
-            namespace_project_edit_blob_path(project.namespace, project,
-                                             tree_join(ref, path),
-                                             link_opts),
-            class: cls
-           ) + after.html_safe
+
+    edit_path = namespace_project_edit_blob_path(project.namespace, project,
+                                     tree_join(ref, path),
+                                     link_opts)
+
+    if !on_top_of_branch?
+      button_tag "Edit", class: "btn btn-default disabled has_tooltip", title: "You can only edit files when you are on a branch", data: { container: 'body' }
+    elsif can_edit_blob?(blob)
+      link_to "Edit", edit_path, class: 'btn btn-small'
+    elsif can?(current_user, :fork_project, project)
+      continue_params = {
+        to:     edit_path,
+        notice: edit_in_new_fork_notice,
+        notice_now: edit_in_new_fork_notice_now
+      }
+      fork_path = namespace_project_fork_path(project.namespace, project, namespace_key:  current_user.namespace.id,
+                                                                          continue:       continue_params)
+
+      link_to "Edit", fork_path, class: 'btn btn-small', method: :post
+    end
+  end
+
+  def modify_file_link(project = @project, ref = @ref, path = @path, label:, action:, btn_class:, modal_type:)
+    return unless current_user
+
+    blob = project.repository.blob_at(ref, path) rescue nil
+
+    return unless blob
+
+    if !on_top_of_branch?
+      button_tag label, class: "btn btn-#{btn_class} disabled has_tooltip", title: "You can only #{action} files when you are on a branch", data: { container: 'body' }
+    elsif blob.lfs_pointer?
+      button_tag label, class: "btn btn-#{btn_class} disabled has_tooltip", title: "It is not possible to #{action} files that are stored in LFS using the web interface", data: { container: 'body' }
+    elsif can_edit_blob?(blob)
+      button_tag label, class: "btn btn-#{btn_class}", 'data-target' => "#modal-#{modal_type}-blob", 'data-toggle' => 'modal'
+    elsif can?(current_user, :fork_project, project)
+      continue_params = {
+        to:     request.fullpath,
+        notice: edit_in_new_fork_notice + " Try to #{action} this file again.",
+        notice_now: edit_in_new_fork_notice_now
+      }
+      fork_path = namespace_project_fork_path(project.namespace, project, namespace_key:  current_user.namespace.id,
+                                                                          continue:       continue_params)
+
+      link_to label, fork_path, class: "btn btn-#{btn_class}", method: :post
+    end
+  end
+
+  def replace_blob_link(project = @project, ref = @ref, path = @path)
+    modify_file_link(
+      project,
+      ref,
+      path,
+      label:      "Replace",
+      action:     "replace",
+      btn_class:  "default",
+      modal_type: "upload"
+    )
+  end
+
+  def delete_blob_link(project = @project, ref = @ref, path = @path)
+    modify_file_link(
+      project,
+      ref,
+      path,
+      label:      "Delete",
+      action:     "delete",
+      btn_class:  "remove",
+      modal_type: "remove"
+    )
   end
 
-  def blob_editable?(blob, project = @project, ref = @ref)
-    !blob.lfs_pointer? && allowed_tree_edit?(project, ref)
+  def can_edit_blob?(blob, project = @project, ref = @ref)
+    !blob.lfs_pointer? && can_edit_tree?(project, ref)
   end
 
   def leave_edit_message
@@ -70,7 +128,7 @@ module BlobHelper
     icon("#{file_type_icon_class('file', mode, name)} fw")
   end
 
-  def blob_viewable?(blob)
+  def blob_text_viewable?(blob)
     blob && blob.text? && !blob.lfs_pointer?
   end
 
diff --git a/app/helpers/tree_helper.rb b/app/helpers/tree_helper.rb
index f448dd0ab61..2ad7c80dae0 100644
--- a/app/helpers/tree_helper.rb
+++ b/app/helpers/tree_helper.rb
@@ -50,24 +50,49 @@ module TreeHelper
     project.repository.branch_names.include?(ref)
   end
 
-  def allowed_tree_edit?(project = nil, ref = nil)
+  def can_edit_tree?(project = nil, ref = nil)
     project ||= @project
     ref ||= @ref
+
     return false unless on_top_of_branch?(project, ref)
 
-    can?(current_user, :push_code, project)
+    can?(current_user, :push_code, project) ||
+      (current_user && current_user.already_forked?(project))
   end
 
   def tree_edit_branch(project = @project, ref = @ref)
-    if allowed_tree_edit?(project, ref)
-      if can_push_branch?(project, ref)
-        ref
-      else
-        project.repository.next_patch_branch
-      end
+    return unless can_edit_tree?(project, ref)
+
+    if can_push_branch?(project, ref)
+      ref
+    else
+      project = tree_edit_project(project)
+      project.repository.next_patch_branch
+    end
+  end
+
+  def tree_edit_project(project = @project)
+    if can?(current_user, :push_code, project)
+      project
+    elsif current_user && current_user.already_forked?(project)
+      current_user.fork_of(project)
     end
   end
 
+  def edit_in_new_fork_notice_now
+    "You're not allowed to make changes to this project directly." +
+      " A fork of this project is being created that you can make changes in, so you can submit a merge request."
+  end
+
+  def edit_in_new_fork_notice
+    "You're not allowed to make changes to this project directly." +
+      " A fork of this project has been created that you can make changes in, so you can submit a merge request."
+  end
+
+  def commit_in_fork_help
+    "A new branch will be created in your fork and a new merge request will be started."
+  end
+
   def tree_breadcrumbs(tree, max_links = 2)
     if @path.present?
       part_path = ""