Merge branch 'jc/1.7.0-push-safety'

* jc/1.7.0-push-safety:
  Refuse deleting the current branch via push
  Refuse updating the current branch in a non-bare repository via push

t/t5516-fetch-push.sh

@@ -12,6 +12,7 @@ mk_empty () {
 	(
 		cd testrepo &&
 		git init &&
+		git config receive.denyCurrentBranch warn &&
 		mv .git/hooks .git/hooks-disabled
 	)
 }