git-fetch: allow updating the current branch in a bare repository.

Sometimes, people have only fetch access into a bare repository
that is used as a back-up location (or a distribution point) but
does not have a push access for networking reasons, e.g. one end
being behind a firewall, and updating the "current branch" in
such a case is perfectly fine.

This allows such a fetch without --update-head-ok, which is a
flag that should never be used by end users otherwise.

Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/git-sh-setup.sh b/git-sh-setup.sh
index 87b939c..7fdc912 100755
--- a/git-sh-setup.sh
+++ b/git-sh-setup.sh
@@ -28,6 +28,14 @@
 	fi
 }
 
+is_bare_repository () {
+	git-repo-config --bool --get core.bare ||
+	case "$GIT_DIR" in
+	.git | */.git) echo false ;;
+	*) echo true ;;
+	esac
+}
+
 if [ -z "$LONG_USAGE" ]
 then
 	LONG_USAGE="Usage: $0 $USAGE"