[PATCH] mmap error handling

I have reviewed all occurrences of mmap() in git and fixed three types
of errors/defects:

1) The result is not checked.
2) The file descriptor is closed if mmap() succeeds, but not when it
fails.
3) Various casts applied to -1 are used instead of MAP_FAILED, which is
specifically defined to check mmap() return value.

[jc: This is a second round of Pavel's patch.  He fixed up the problem
that close() potentially clobbering the errno from mmap, which
the first round had.]

Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

local-pull.c

@@ -54,7 +54,7 @@ int fetch(unsigned char *sha1)
 		}
 		map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, ifd, 0);
 		close(ifd);
-		if (-1 == (int)(long)map) {
+		if (map == MAP_FAILED) {
 			fprintf(stderr, "cannot mmap %s\n", filename);
 			return -1;
 		}