Read expected buffer size (#17409) (#17430)

Backport of #17409

* Read expected buffer size.

* Changed name.

modules/git/blob.go

@@ -12,6 +12,7 @@ import (
 	"io/ioutil"
 
 	"code.gitea.io/gitea/modules/typesniffer"
+	"code.gitea.io/gitea/modules/util"
 )
 
 // This file contains common functions between the gogit and !gogit variants for git Blobs
@@ -29,7 +30,7 @@ func (b *Blob) GetBlobContent() (string, error) {
 	}
 	defer dataRc.Close()
 	buf := make([]byte, 1024)
-	n, _ := dataRc.Read(buf)
+	n, _ := util.ReadAtMost(dataRc, buf)
 	buf = buf[:n]
 	return string(buf), nil
 }