Add native git fetch support

Current implementation uses JGit to fetch refs from remote. JGit fetch
implementation performance is lower then native git fetch. Add support
for native git to workaround performance issues.

Feature: Issue 11605
Change-Id: Ib1f018a339e3fb13be83652237c8a4fb1fd4f1fa
12 files changed
tree: 54b607302c9b5f5a617b9b72c394402fceb33e9d
  1. BUILD
  2. Jenkinsfile
  4. src/