rerere: replace strcpy with xsnprintf

This shouldn't overflow, as we are copying a sha1 hex into a
41-byte buffer. But it does not hurt to use a bound-checking
function, which protects us and makes auditing for overflows
easier.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: peff

rerere.c

@@ -50,7 +50,7 @@ static int has_rerere_resolution(const struct rerere_id *id)
 static struct rerere_id *new_rerere_id_hex(char *hex)
 {
 	struct rerere_id *id = xmalloc(sizeof(*id));
-	strcpy(id->hex, hex);
+	xsnprintf(id->hex, sizeof(id->hex), "%s", hex);
 	return id;
 }
 
@@ -900,7 +900,7 @@ int rerere_forget(struct pathspec *pathspec)
 static struct rerere_id *dirname_to_id(const char *name)
 {
 	static struct rerere_id id;
-	strcpy(id.hex, name);
+	xsnprintf(id.hex, sizeof(id.hex), "%s", name);
 	return &id;
 }