[PATCH] strtoul_ui: actually report error in case of negative input

[Max Kirillov <max@max630.net>]

If s == "-1" and CPU is i386, then none of the checks is triggered, including
the last "(unsigned int) ul != ul", because ul == 2**32 - 1, which fits into
"unsigned int".

Fix it by changing the last check to trigger earlier, as soon as it
becomes bigger than INT_MAX.

Signed-off-by: Max Kirillov <max@max630.net>
---
This caused failure of "%(contents:lines=-1)` should fail" case from
t6302-for-each-ref-filter.sh for me in pu. Don't know why nobody has noticed
it. It did not trigger errno, instead wrapping the value. I have libc6 2.13
(debian wheezy)

Still can be fooled with carefully chosen negative input. For i386 it's
between INT_MIN and something like -UINT_MIN

Adding people from the commit which uses the function.
 git-compat-util.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index f649e81..1c0229b 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -815,7 +815,7 @@ static inline int strtoul_ui(char const *s, int base, unsigned int *result)
 
 	errno = 0;
 	ul = strtoul(s, &p, base);
-	if (errno || *p || p == s || (unsigned int) ul != ul)
+	if (errno || *p || p == s || ul > (unsigned long) INT_MAX)
 		return -1;
 	*result = ul;
 	return 0;
-- 
2.3.4.2801.g3d0809b