implement assure_distr and use it

bin/epm-install

@@ -680,6 +680,7 @@ epm_print_install_names_command()
 epm_install()
 {
     if tasknumber "$pkg_names" >/dev/null ; then
+        assure_distr ALTLinux "install with task number"
         assure_exists apt-repo
         sudocmd apt-repo test $(tasknumber "$pkg_names")
         return

bin/epm-remove

@@ -244,6 +244,7 @@ epm_remove()
 
 	local tn=$(tasknumber "$pkg_names")
 	if [ -n "$tn" ] ; then
+		assure_distr ALTLinux "remove with task number"
 		assure_exists apt-repo
 		pkg_names=$(showcmd apt-repo list $tn)
 		#docmd epm remove $dryrun

bin/epm-sh-functions

@@ -549,3 +549,10 @@ is_active_systemd()
 	# shellcheck disable=SC2009
 	ps ax | grep '[s]ystemd' | grep -q -v 'systemd-udev'
 }
+
+assure_distr()
+{
+	local TEXT="this option"
+	[ -n "$2" ] && TEXT="$2"
+	[ "$DISTRNAME" = "$1" ] || fatal "$TEXT supported only for $1 distro"
+}