Upgrade patch to detect hunks that start after a false start.

Imagine a hunk that starts with a blank line, but the site to patch starts
with two blank lines.  Before we'd read the first blank line, think it was the
start of the hunk and buffer it, read the second blank line, notice that it
didn't match the second line of the hunk, and discard _both_ buffered lines of
context (writing them to the output file) without checking that one of the
later context lines might have been the real start of the hunk.

Make it re-check the rest of the buffered context for matches each time it
discards a line of buffered context.

2 files changed, 8 insertions, 2 deletions

diff --git a/lib/lib.h b/lib/lib.h
index cfbeeb3a..70c0c48d 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -27,7 +27,7 @@ struct double_list {
 
 void llist_free(void *list, void (*freeit)(void *data));
 void *llist_pop(void *list);  // actually void **list, but the compiler's dumb
-void dlist_add(struct double_list **list, char *data);
+struct double_list *dlist_add(struct double_list **list, char *data);
 
 // args.c
 void get_optflags(void);
diff --git a/lib/llist.c b/lib/llist.c
index 4f9bc220..9adb64e0 100644
--- a/lib/llist.c
+++ b/lib/llist.c
@@ -14,6 +14,10 @@ void llist_free(void *list, void (*freeit)(void *data))
 	while (list) {
 		void *pop = llist_pop(&list);
 		if (freeit) freeit(pop);
+		else free(pop);
+
+		// End doubly linked list too.
+		if (list==pop) break;
 	}
 }
 
@@ -32,7 +36,7 @@ void *llist_pop(void *list)
 }
 
 // Add an entry to the end off a doubly linked list
-void dlist_add(struct double_list **list, char *data)
+struct double_list *dlist_add(struct double_list **list, char *data)
 {
 	struct double_list *line = xmalloc(sizeof(struct double_list));
 
@@ -43,4 +47,6 @@ void dlist_add(struct double_list **list, char *data)
 		(*list)->prev->next = line;
 		(*list)->prev = line;
 	} else *list = line->next = line->prev = line;
+
+	return line;
 }