[PATCH] dir.c: clean the entire struct in clear_exclude_list()

Make sure "el" can be reuseable again. The problem was el->alloc is
not cleared and may cause segfaults next time because add_exclude()
thinks el->excludes (being NULL) has enough space. Just clear the
entire struct to be safe.

Signed-off-by: Nguyễn Thái Ngọc Duy <redacted>
---
 This was needed in the worktree config split series because the same
 exclude_list could be reused. But that series is changing and will not
 need exclude_list any more. So instead of dropping this patch, I
 submit it separately. It's a good fix anyway.

 dir.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/dir.c b/dir.c
index d2a8f06..b8b4576 100644
--- a/dir.c
+++ b/dir.c

@@ -564,9 +564,7 @@ void clear_exclude_list(struct exclude_list *el)
 	free(el->excludes);
 	free(el->filebuf);
 
-	el->nr = 0;
-	el->excludes = NULL;
-	el->filebuf = NULL;
+	memset(el, 0, sizeof(*el));
 }
 
 static void trim_trailing_spaces(char *buf)

-- 
2.3.0.rc1.137.g477eb31