Fix what to do and how to detect when hardlinking fails

Recent FAT workaround caused compilation trouble on OpenBSD;
different platforms use different error codes when we try to
hardlink the temporary file to its final location.  Existing
Coda hack also checks its own error code, but the thing is,
the case we care about is if link failed for a reason other
than that the final file has already existed (which would be
normal, or it could mean collision).  So just check the error
code against EEXIST.

Signed-off-by: Junio C Hamano <junkio@cox.net>

sha1_file.c

@@ -1232,19 +1232,20 @@ static int link_temp_to_file(const char *tmpfile, char *filename)
 int move_temp_to_file(const char *tmpfile, char *filename)
 {
 	int ret = link_temp_to_file(tmpfile, filename);
-	if (ret) {
-		/*
-		 * Coda hack - coda doesn't like cross-directory links,
-		 * so we fall back to a rename, which will mean that it
-		 * won't be able to check collisions, but that's not a
-		 * big deal.
-		 *
-		 * The same holds for FAT formatted media.
-		 *
-		 * When this succeeds, we just return 0. We have nothing
-		 * left to unlink.
-		 */
-		if ((ret == EXDEV || ret == ENOTSUP) && !rename(tmpfile, filename))
+
+	/*
+	 * Coda hack - coda doesn't like cross-directory links,
+	 * so we fall back to a rename, which will mean that it
+	 * won't be able to check collisions, but that's not a
+	 * big deal.
+	 *
+	 * The same holds for FAT formatted media.
+	 *
+	 * When this succeeds, we just return 0. We have nothing
+	 * left to unlink.
+	 */
+	if (ret && ret != EEXIST) {
+		if (!rename(tmpfile, filename))
 			return 0;
 		ret = errno;
 	}