Expand/Collapse Files and Blob Excerpt while Reviewing/Comparing code (#8924)

* update #8659 fold/unfold code diffs

* add fold button style

* update #8659 implement expand up/down codes (blob excerpt)

* fix golint errors

* fix expand direction

* remove debug message

* update css style for blob exceprt

* fix typo in comment

* update style sheet with less

* update expect diff (add SectionInfo)

* update #8942 accept suggested change (fix typo)

* close reader and check file type before get tail section

* adjust button position and check file type before insert fold button

* move index js to web_src

* merge index.js with master

* generate index.js

* update js coding style

modules/git/blob.go

@@ -6,6 +6,7 @@
 package git
 
 import (
+	"bytes"
 	"encoding/base64"
 	"io"
 	"io/ioutil"
@@ -50,6 +51,28 @@ func (b *Blob) GetBlobContent() (string, error) {
 	return string(buf), nil
 }
 
+// GetBlobLineCount gets line count of lob as raw text
+func (b *Blob) GetBlobLineCount() (int, error) {
+	reader, err := b.DataAsync()
+	if err != nil {
+		return 0, err
+	}
+	defer reader.Close()
+	buf := make([]byte, 32*1024)
+	count := 0
+	lineSep := []byte{'\n'}
+	for {
+		c, err := reader.Read(buf)
+		count += bytes.Count(buf[:c], lineSep)
+		switch {
+		case err == io.EOF:
+			return count, nil
+		case err != nil:
+			return count, err
+		}
+	}
+}
+
 // GetBlobContentBase64 Reads the content of the blob with a base64 encode and returns the encoded string
 func (b *Blob) GetBlobContentBase64() (string, error) {
 	dataRc, err := b.DataAsync()