Merge branch 'search-git-grep' into 'master'

Implement faster search of code (via git grep)

Much faster than iterating over each file using rugged.

Performance compare for Linux repository using keyword `sha`:

```
OLD: 250 seconds
NEW: 9 seconds
```

See merge request !957

CHANGELOG

@@ -43,6 +43,7 @@ v 7.13.0 (unreleased)
   - Redesign project page. Show README as default instead of activity. Move project activity to separate page
   - Make left menu more hierarchical and less contextual by adding back item at top
   - A fork can’t have a visibility level that is greater than the original project.
+  - Faster code search in repository and wiki. Fixes search page timeout for big repositories 
 
 v 7.12.2
   - Correctly show anonymous authorized applications under Profile > Applications.

app/models/repository.rb

@@ -431,6 +431,40 @@ class Repository
     end
   end
 
+  def search_files(query, ref)
+    offset = 2
+    args = %W(git grep -i -n --before-context #{offset} --after-context #{offset} #{query} #{ref || root_ref})
+    Gitlab::Popen.popen(args, path_to_repo).first.scrub.split(/^--$/)
+  end
+
+  def parse_search_result(result)
+    ref = nil
+    filename = nil
+    startline = 0
+
+    lines = result.lines
+    lines.each_with_index do |line, index|
+      if line =~ /^.*:.*:\d+:/
+        ref, filename, startline = line.split(':')
+        startline = startline.to_i - index
+        break
+      end
+    end
+
+    data = lines.map do |line|
+      line.sub(ref, '').sub(filename, '').sub(/^:-\d+-/, '').sub(/^::\d+:/, '')
+    end
+
+    data = data.join("")
+
+    OpenStruct.new(
+      filename: filename,
+      ref: ref,
+      startline: startline,
+      data: data
+    )
+  end
+
   private
 
   def cache

app/views/search/results/_blob.html.haml

+- blob = @project.repository.parse_search_result(blob)
 .blob-result
   .file-holder
     .file-title

app/views/search/results/_wiki_blob.html.haml

+- wiki_blob = @project.repository.parse_search_result(wiki_blob)
 .blob-result
   .file-holder
     .file-title

spec/models/repository_spec.rb

@@ -47,4 +47,28 @@ describe Repository do
       it { is_expected.to be_falsey }
     end
   end
+
+  describe "search_files" do
+    let(:results) { repository.search_files('feature', 'master') }
+    subject { results }
+
+    it { is_expected.to be_an Array }
+
+    describe 'result' do
+      subject { results.first }
+
+      it { is_expected.to be_an String }
+      it { expect(subject.lines[2]).to eq("master:CHANGELOG:188:  - Feature: Replace teams with group membership\n") }
+    end
+
+    describe 'parsing result' do
+      subject { repository.parse_search_result(results.first) }
+
+      it { is_expected.to be_an OpenStruct }
+      it { expect(subject.filename).to eq('CHANGELOG') }
+      it { expect(subject.ref).to eq('master') }
+      it { expect(subject.startline).to eq(186) }
+      it { expect(subject.data.lines[2]).to eq("  - Feature: Replace teams with group membership\n") }
+    end
+  end
 end