git stash: make sure that .git/logs/refs/ exists

If the user has not activated reflogs, or if nothing has been recorded
yet (as is the case directly after cloning), said directory may not
exist yet.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

git-stash.sh

@@ -262,6 +262,7 @@ save_stash () {
 		clear_stash || die "$(gettext "Cannot initialize stash")"
 
 	create_stash "$stash_msg" $untracked
+	mkdir -p "$GIT_DIR/logs/${ref_stash%/*}"
 	store_stash -m "$stash_msg" -q $w_commit ||
 	die "$(gettext "Cannot save the current status")"
 	say Saved working directory and index state "$stash_msg"