info/grafts: allow trailing whitespaces at the end of line

When creating an info/grafts under windows, one typically gets a CRLF file.
There is no good reason to forbid trailing CR at the end of the line (for
that matter, any trailing whitespaces); the code allowed only LF simply
because that was good enough for the platforms with LF line endings.

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

commit.c

@@ -136,8 +136,8 @@ struct commit_graft *read_graft_line(char *buf, int len)
 	int i;
 	struct commit_graft *graft = NULL;
 
-	if (buf[len-1] == '\n')
-		buf[--len] = 0;
+	while (len && isspace(buf[len-1]))
+		buf[--len] = '\0';
 	if (buf[0] == '#' || buf[0] == '\0')
 		return NULL;
 	if ((len + 1) % 41) {