diff --git a/app/assets/stylesheets/views/diff.css.sass b/app/assets/stylesheets/views/diff.css.sass
index ca13f297d..9d32cfe4a 100644
--- a/app/assets/stylesheets/views/diff.css.sass
+++ b/app/assets/stylesheets/views/diff.css.sass
@@ -78,8 +78,5 @@ table.table.diff.inline
         margin-top: 5px
 
 div.file div.top
-  height: 28px
+  min-height: 28px
   background: #ededed
-
-  .pull-left, .pull-right
-    margin: 6px 10px 0px 10px
diff --git a/app/helpers/diff_helper.rb b/app/helpers/diff_helper.rb
index f39194fad..f1353f461 100644
--- a/app/helpers/diff_helper.rb
+++ b/app/helpers/diff_helper.rb
@@ -1,4 +1,7 @@
 module DiffHelper
+  MAX_FILES_WITHOUT_COLLAPSE = 25
+  MAX_LINES_WITHOUT_COLLAPSE = 50
+
   def render_diff_stats(stats)
     path = @pull.try(:id) ? polymorphic_path([@project, @pull]) : ''
 
@@ -20,7 +23,7 @@ module DiffHelper
   end
 
   def wrap_header_list(stats, list)
-    is_stats_open = stats.count <= 25 ? 'in' : ''
+    is_stats_open = stats.count <= MAX_FILES_WITHOUT_COLLAPSE ? 'in' : ''
     res = ["<div class='panel-group' id='diff_header' role='tablist' aria-multiselectable='false'>"]
       res << "<div class='panel panel-default'>"
         res << "<div class='panel-heading' role='tab' id='heading'>"
diff --git a/app/views/projects/git/commits/diff.html.haml b/app/views/projects/git/commits/diff.html.haml
deleted file mode 100644
index 4eb8d28dd..000000000
--- a/app/views/projects/git/commits/diff.html.haml
+++ /dev/null
@@ -1,40 +0,0 @@
--title = "#{t('diff')} #{shortest_hash_id @commit1.id}...#{shortest_hash_id @commit.id}"
--set_meta_tags title: [title_object(@project), title]
-=render 'submenu'
-
-%h3=title
-.both
-#repo-wrapper
-  .leftside
-    -total_additions = @stats.inject(0) {|sum, n| sum + n.additions}
-    -total_deletions = @stats.inject(0) {|sum, n| sum + n.deletions}
-    %h5= t("layout.projects.diff_show_header",
-      files:     t("layout.projects.commit_files_count",     count: @stats.count),
-      additions: t("layout.projects.commit_additions_count", count: total_additions),
-      deletions: t("layout.projects.commit_deletions_count", count: total_deletions))
-  .both
-  -begin
-    =render_diff_stats @stats
-    - Grit::Commit.diff(@project.repo, @common_ancestor.id, @commit.id).each_with_index do |commit_diff, diff_counter|
-      - commit_id = commit_diff.deleted_file ? @common_ancestor.id : @commit.id
-      .file
-        %a{name: "diff-#{diff_counter}"}
-        .top
-          .l= h(commit_diff.a_path.rtruncate 120)
-          - if commit_diff.b_path.present?
-            .r= link_to "view file @ #{short_hash_id(commit_id)}", blob_path(@project, commit_id, commit_diff.b_path)
-          .clear
-        -if commit_diff.diff.present?
-          .diff_data
-            - blob = @project.repo.tree(commit_id) / commit_diff.b_path
-            - if blob.render_as == :image
-              %table.diff.inline{ cellspacing: 0, cellpadding: 0 }
-                %tr
-                  %td.lines
-                  %td.blob.diff-image
-                    %span.diff-image
-                      %img{ src: "data:#{blob.mime_type};base64,#{Base64.encode64(blob.data)}",
-                            style: 'max-width: 600px;' }
-            = render_diff(commit_diff, diff_counter: diff_counter) unless blob.binary?
-  - rescue Grit::Git::GitTimeout
-    %p= t 'layout.git.repositories.commit_diff_too_big'
diff --git a/app/views/projects/git/commits/diff.html.slim b/app/views/projects/git/commits/diff.html.slim
new file mode 100644
index 000000000..2546aac54
--- /dev/null
+++ b/app/views/projects/git/commits/diff.html.slim
@@ -0,0 +1,46 @@
+-title = "#{t('diff')} #{shortest_hash_id @commit1.id}...#{shortest_hash_id @commit.id}"
+-set_meta_tags title: [title_object(@project), title]
+== render 'submenu'
+
+h3= title
+
+#repo-wrapper
+  .leftside
+    -total_additions = @stats.inject(0) {|sum, n| sum + n.additions}
+    -total_deletions = @stats.inject(0) {|sum, n| sum + n.deletions}
+    h5= t("layout.projects.diff_show_header",
+      files:     t("layout.projects.commit_files_count",     count: @stats.count),
+      additions: t("layout.projects.commit_additions_count", count: total_additions),
+      deletions: t("layout.projects.commit_deletions_count", count: total_deletions))
+
+  -begin
+    == render_diff_stats @stats
+    - Grit::Commit.diff(@project.repo, @common_ancestor.id, @commit.id).each_with_index do |commit_diff, diff_counter|
+      - commit_id = commit_diff.deleted_file ? @common_ancestor.id : @commit.id
+      .file
+        a name = "diff-#{diff_counter}"
+        .top
+          .pull-left
+            a[ type          = 'button'
+                    class         = 'btn btn-danger'
+                    data-toggle   = 'collapse'
+                    data-target   = "#demo"
+                    aria-expanded = 'true'
+                    aria-controls = "demo" ]
+              = h(commit_diff.a_path.rtruncate 120)
+          - if commit_diff.b_path.present?
+            .pull-right= link_to "view file @ #{short_hash_id(commit_id)}", blob_path(@project, commit_id, commit_diff.b_path)
+          .clearfix
+        -if commit_diff.diff.present?
+          .diff_data
+            - blob = @project.repo.tree(commit_id) / commit_diff.b_path
+            - if blob.render_as == :image
+              table.table.diff.inline.table-bordered[ cellspacing = 0 cellpadding = 0 ]
+                tr
+                  td.diff-image
+                    span.diff-image
+                      img[ src   = "data:#{blob.mime_type};base64,#{Base64.encode64(blob.data)}"
+                           style = 'max-width: 600px;' ]
+            == render_diff(commit_diff, diff_counter: diff_counter) unless blob.binary?
+  - rescue Grit::Git::GitTimeout
+    p= t 'layout.git.repositories.commit_diff_too_big'
diff --git a/app/views/projects/pull_requests/_pull_diff.html.slim b/app/views/projects/pull_requests/_pull_diff.html.slim
index 75649c7d3..f490d6007 100644
--- a/app/views/projects/pull_requests/_pull_diff.html.slim
+++ b/app/views/projects/pull_requests/_pull_diff.html.slim
@@ -1,15 +1,25 @@
-- commit_id = pull_diff.deleted_file ? @pull.to_commit.id : @pull.from_commit.id
-.file
-  a name = "diff-#{pull_diff_counter}"
+- commit_id            = pull_diff.deleted_file ? @pull.to_commit.id : @pull.from_commit.id
+- diff_counter         = "diff-#{pull_diff_counter}"
+- diff_counter_content = "#{diff_counter}_content"
+.file.offset20
+  a name = diff_counter
   .top
-    .pull-left= h(pull_diff.renamed_file ? "#{pull_diff.a_path.rtruncate 60}=>#{pull_diff.b_path.rtruncate 60}" : pull_diff.b_path.rtruncate(120))
+    button.btn.btn-link.pull-left[ type = 'button'
+                data-toggle   = 'collapse'
+                data-target   = "##{diff_counter_content}"
+                aria-expanded = 'true'
+                aria-controls = diff_counter_content ]
+        = h(pull_diff.renamed_file ? "#{pull_diff.a_path.rtruncate 60}=>#{pull_diff.b_path.rtruncate 60}" : pull_diff.b_path.rtruncate(120))
     - if @pull.from_project.present?
-      .pull-right= link_to "view file @ #{short_hash_id(commit_id)}", blob_path(@pull.from_project, commit_id, pull_diff.b_path)
+      button.btn.btn-link.pull-right
+        = link_to "view file @ #{short_hash_id(commit_id)}", blob_path(@pull.from_project, commit_id, pull_diff.b_path)
     .clearfix
 
   -if pull_diff.diff.present?
-    .diff_data
-      - blob = @pull.repo.tree(commit_id) / pull_diff.b_path
+    - blob = @pull.repo.tree(commit_id) / pull_diff.b_path
+    - is_file_open = 'in' if !blob.binary? && pull_diff.diff.split("\n").count <= DiffHelper::MAX_LINES_WITHOUT_COLLAPSE
+
+    .diff_data.collapse[ id = diff_counter_content class = is_file_open ]
       - if blob.render_as == :image
         table.table.diff.inline.table-bordered[ cellspacing = 0 cellpadding = 0 ]
           tr