Merge branch 'js/completion-hide-not-a-repo'

Some internal error messages leaked out of the bash completion when
typing "git cmd <TAB>" and the machinery tried to complete
refnames.

* js/completion-hide-not-a-repo:
  completion: silence "fatal: Not a git repository" error

contrib/completion/git-completion.bash

@@ -384,7 +384,8 @@ __git_refs ()
 		;;
 	*)
 		echo "HEAD"
-		git for-each-ref --format="%(refname:short)" -- "refs/remotes/$dir/" | sed -e "s#^$dir/##"
+		git for-each-ref --format="%(refname:short)" -- \
+			"refs/remotes/$dir/" 2>/dev/null | sed -e "s#^$dir/##"
 		;;
 	esac
 }