worktree: make add <path> <branch> dwim

diff --git a/list.h b/list.h
index f65edce14888a84ef0860edf8ec7523470ed2468..eb601192f4ca9a6af126c82f4c2a24cb9145009d 100644 (file)
--- a/list.h
+++ b/list.h
@@ -36,6 +36,8 @@ struct list_head {
        struct list_head *next, *prev;
 };
 
+/* avoid conflicts with BSD-only sys/queue.h */
+#undef LIST_HEAD
 /* Define a variable with the head and tail of the list. */
 #define LIST_HEAD(name) \
        struct list_head name = { &(name), &(name) }
@@ -161,4 +163,42 @@ static inline void list_replace_init(struct list_head *old,
        INIT_LIST_HEAD(old);
 }
 
+/*
+ * This is exactly the same as a normal list_head, except that it can be
+ * declared volatile (e.g., if you have a list that may be accessed from signal
+ * handlers).
+ */
+struct volatile_list_head {
+       volatile struct volatile_list_head *next, *prev;
+};
+
+#define VOLATILE_LIST_HEAD(name) \
+       volatile struct volatile_list_head name = { &(name), &(name) }
+
+static inline void __volatile_list_del(volatile struct volatile_list_head *prev,
+                                      volatile struct volatile_list_head *next)
+{
+       next->prev = prev;
+       prev->next = next;
+}
+
+static inline void volatile_list_del(volatile struct volatile_list_head *elem)
+{
+       __volatile_list_del(elem->prev, elem->next);
+}
+
+static inline int volatile_list_empty(volatile struct volatile_list_head *head)
+{
+       return head == head->next;
+}
+
+static inline void volatile_list_add(volatile struct volatile_list_head *newp,
+                                    volatile struct volatile_list_head *head)
+{
+       head->next->prev = newp;
+       newp->next = head->next;
+       newp->prev = head;
+       head->next = newp;
+}
+
 #endif /* LIST_H */