one of the documented procedures in this installation of the ACS
apm_ignore_file_p   path
What it does:
Return 1 if $path should, in general, be ignored for package operations. Currently, a file is ignored if it is a backup file or a CVS directory.
Defined in: /web/philip/packages/acs-core/apm-procs.tcl

Source code:

    set tail [file tail $path]
    if { [apm_backup_file_p $tail] } {
	return 1
    if { [string equal $tail "CVS"] } {
	return 1
    return 0