one of the documented procedures in this installation of the ACS
apm_package_info_file_path   package_key
What it does:
Returns the path to a .info file in a package directory, or throws an error if none exists. Currently, only $package_key.info is recognized as a specification file.
Defined in: /web/philip/packages/acs-core/apm-procs.tcl

Source code:

    set path "[acs_package_root_dir $package_key]/$package_key.info"
    if { [file exists $path] } {
	return $path
    error "The /packages/$package_key directory does not contain a package specification file ($package_key.info)."