sha1_file.c (write_sha1_from_fd): Detect close failure.

I stumbled across this in the context of the fchmod 0444 patch.
At first, I was going to unlink and call error like the two subsequent
tests do, but a failed write (above) provokes a "die", so I made
this do the same.  This is testing for a write failure, after all.

Signed-off-by: Jim Meyering <jim@meyering.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

sha1_file.c

@@ -2155,7 +2155,8 @@ int write_sha1_from_fd(const unsigned char *sha1, int fd, char *buffer,
 	inflateEnd(&stream);
 
 	fchmod(local, 0444);
-	close(local);
+	if (close(local) != 0)
+		die("unable to write sha1 file");
 	SHA1_Final(real_sha1, &c);
 	if (ret != Z_STREAM_END) {
 		unlink(tmpfile);