A loose object is not corrupt if it cannot be read due to EMFILE

"git fsck" bails out with a claim that a loose object that cannot be
read but exists on the filesystem to be corrupt, which is wrong when
read_object() failed due to e.g. EMFILE.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

sha1_file.c

@@ -2090,16 +2090,21 @@ void *read_sha1_file_repl(const unsigned char *sha1,
 			  const unsigned char **replacement)
 {
 	const unsigned char *repl = lookup_replace_object(sha1);
-	void *data = read_object(repl, type, size);
+	void *data;
 	char *path;
 	const struct packed_git *p;
 
+	errno = 0;
+	data = read_object(repl, type, size);
 	if (data) {
 		if (replacement)
 			*replacement = repl;
 		return data;
 	}
 
+	if (errno != ENOENT)
+		die_errno("failed to read object %s", sha1_to_hex(sha1));
+
 	/* die if we replaced an object with one that does not exist */
 	if (repl != sha1)
 		die("replacement %s not found for %s",