possibility to add specific group list to config

[fschuett]

Hallo,
I have a special problem, I want to use your module to sync only some specific moodle cohorts but not all cohorts found in ldap.
So I added a patch to optionally create a list of groups, which is then used as a filter for ldap_get_grouplist. If you find this option useful, please add it to the code, maybe others could use this filter, too.

I attach the patch to this post.

..diff -up moodle/local/ldap/locallib.php.orig moodle/local/ldap/locallib.php
..--- moodle/local/ldap/locallib.php.orig 2020-07-20 09:53:01.373282357 +0200
..+++ moodle/local/ldap/locallib.php 2020-07-20 10:15:22.966568914 +0200
..@@ -66,6 +66,7 @@ class local_ldap extends auth_plugin_lda
..
.. // Get my specific settings.
.. $extra = get_config('local_ldap');
..+ $this->merge_config($extra, 'group_list','');
.. $this->merge_config($extra, 'group_attribute', 'cn');
.. $this->merge_config($extra, 'group_class', 'groupOfNames');
.. $this->merge_config($extra, 'process_nested_groups', 0);
..@@ -675,7 +676,14 @@ class local_ldap extends auth_plugin_lda
.. public function sync_cohorts_by_group() {
.. global $DB;
..
..- $ldapgroups = $this->ldap_get_grouplist();
..+ $grouplist = $this->config->group_list;
..+ if (! empty($grouplist) && $grouplist != "") {
..+ $filter = "&(" . $this->config->group_attribute . "=)(objectclass=" . $this->config->group_class . ")";
..+ $groupfilter = $filter . "(|(cn=".implode(")(cn=",explode(",",$grouplist))."))";
..+ $ldapgroups = $this->ldap_get_grouplist("(".$groupfilter.")");
..+ } else {
..+ $ldapgroups = $this->ldap_get_grouplist();
..+ }
.. foreach ($ldapgroups as $groupname) {
.. if (!$cohort = $DB->get_record('cohort', array('idnumber' => $groupname), '')) {
.. if (empty($this->config->cohort_synching_ldap_groups_autocreate_cohorts)) {
..diff -up moodle/local/ldap/settings.php.orig moodle/local/ldap/settings.php
..--- moodle/local/ldap/settings.php.orig 2020-06-15 17:07:02.000000000 +0200
..+++ moodle/local/ldap/settings.php 2020-07-20 10:01:48.490646460 +0200
..@@ -27,6 +27,12 @@ defined('MOODLE_INTERNAL') || die;
.. if ($hassiteconfig) {
.. $settings = new admin_settingpage('local_ldap', get_string('pluginname', 'local_ldap'));
..
..+ $name = 'group_list';
..+ $title = 'Group list';
..+ $description = 'Comma separated list of groups to synchronize';
..+ $setting = new admin_setting_configtext('local_ldap/'.$name, $title, $description, '');
..+ $settings->add($setting);
..+
.. $settings->add(new admin_setting_heading('synccohortgroup',
.. get_string('synccohortgroup', 'local_ldap'),
.. get_string('synccohortgroup_info', 'local_ldap')));
..