Document current cvsexportcommit limitations.

Since there is no bugtracker that I know of, let's just use the scripts
themselves to document their limitations.

Signed-off-by: Yann Dirson <ydirson@altern.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-cvsexportcommit.perl

@@ -1,5 +1,12 @@
 #!/usr/bin/perl -w
 
+# Known limitations:
+# - cannot add or remove binary files
+# - cannot add parent directories when needed
+# - does not propagate permissions
+# - tells "ready for commit" even when things could not be completed
+#   (eg addition of a binary file)
+
 use strict;
 use Getopt::Std;
 use File::Temp qw(tempdir);