git-fsck-cache: be stricter about "tree" objects

In particular, warn about things like zero-padding of the mode bits,
which is a big no-no, since it makes otherwise identical trees have
different representations (and thus different SHA1 numbers).

Also make the warnings more regular.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/tree.h b/tree.h
index 74fe09d..ae61bcc 100644
--- a/tree.h
+++ b/tree.h
@@ -10,6 +10,7 @@
 	unsigned directory : 1;
 	unsigned executable : 1;
 	unsigned symlink : 1;
+	unsigned zeropad : 1;
 	unsigned int mode;
 	char *name;
 	union {