update git book link to v2

Author: eshirvana

templates/repo/empty.tmpl

@@ -24,7 +24,7 @@
 					</h4>
 					<div class="ui attached guide table segment empty-repo-guide">
 						<div class="item">
-							<h3>{{ctx.Locale.Tr "repo.clone_this_repo"}} <small>{{ctx.Locale.Tr "repo.clone_helper" "http://git-scm.com/book/en/Git-Basics-Getting-a-Git-Repository"}}</small></h3>
+							<h3>{{ctx.Locale.Tr "repo.clone_this_repo"}} <small>{{ctx.Locale.Tr "repo.clone_helper" "http://git-scm.com/book/en/v2/Git-Basics-Getting-a-Git-Repository"}}</small></h3>
 
 							<div class="repo-button-row">
 								{{if and .CanWriteCode (not .Repository.IsArchived)}}