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

@@ -229,6 +229,7 @@ save_stash () {
 	create_stash "$stash_msg" $untracked
 
 	# Make sure the reflog for stash is kept.
+	mkdir -p "$GIT_DIR/logs/${ref_stash%/*}"
 	: >>"$GIT_DIR/logs/$ref_stash"
 
 	git update-ref -m "$stash_msg" $ref_stash $w_commit ||