cache-tree: replace a sscanf() by two strtol() calls

On one of my systems, sscanf() first calls strlen() on the buffer. But
this buffer is not terminated by NUL. So git crashed.

strtol() does not share that problem, as it stops reading after the
first non-digit.

[jc: original patch was wrong and did not read the cache-tree
 structure correctly; this has been fixed up and tested minimally
 with fsck-objects. ]

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

cache-tree.c

@@ -440,6 +440,8 @@ static struct cache_tree *read_one(const char **buffer, unsigned long *size_p)
 {
 	const char *buf = *buffer;
 	unsigned long size = *size_p;
+	const char *cp;
+	char *ep;
 	struct cache_tree *it;
 	int i, subtree_nr;
 
@@ -453,7 +455,14 @@ static struct cache_tree *read_one(const char **buffer, unsigned long *size_p)
 		goto free_return;
 	buf++; size--;
 	it = cache_tree();
-	if (sscanf(buf, "%d %d\n", &it->entry_count, &subtree_nr) != 2)
+
+	cp = buf;
+	it->entry_count = strtol(cp, &ep, 10);
+	if (cp == ep)
+		goto free_return;
+	cp = ep;
+	subtree_nr = strtol(cp, &ep, 10);
+	if (cp == ep)
 		goto free_return;
 	while (size && *buf && *buf != '\n') {
 		size--;