Implemented Check for updates which removs the last shell exec from web ui, and reimplemented db_update switch to update_cli.php

cron/update_check.php

@@ -0,0 +1,81 @@
+<?php
+
+/*
+ * ITFlow - Update check job
+ *
+ * Asks the git remote whether a newer release exists and stores the answer. Nothing in the
+ * web tier shells out any more, so this is the only place the question gets asked: the
+ * Update page and the nightly notification both read what this job wrote.
+ *
+ * Check Now on Maintenance > Update sets cron_job_run_now on this job rather than checking
+ * inside the request - same mechanism as Queue Update, and the page shows "Checking" until
+ * the dispatcher consumes the flag.
+ *
+ * Safe to run twice: it reads and overwrites, and changes nothing outside the three settings
+ * columns it owns.
+ */
+
+// Set working directory to the directory this cron script lives at.
+chdir(dirname(__FILE__));
+
+// Ensure we're running from command line
+if (php_sapi_name() !== 'cli') {
+    die("This script must be run from the command line.\n");
+}
+
+// Prevent overlapping runs of this script
+$cron_lock_script = __FILE__;
+require_once "includes/cron_lock.php";
+
+require_once "../config.php";
+
+// Set Timezone
+require_once "../includes/inc_set_timezone.php";
+require_once "../functions.php";
+
+$update_check_settings = mysqli_fetch_assoc(mysqli_query($mysqli, "SELECT config_enable_cron FROM settings WHERE company_id = 1"));
+
+$config_enable_cron = intval($update_check_settings['config_enable_cron'] ?? 0);
+
+if ($config_enable_cron == 0) {
+    cronJobStop("Cron: is not enabled\n");
+}
+
+// An install whose files are newer than its schema reaches this job before the migration
+// that adds the columns has run. Asking for them would throw
+if (!settingsColumnExists($mysqli, 'config_update_latest_commit')) {
+    cronJobStop("The database update has not been applied yet\n");
+}
+
+// A zip-drop install has no remote to ask. Not a failure - there is simply nothing to check
+if (!file_exists("../.git")) {
+    cronJobStop("Not a git checkout - there is no remote to check against\n");
+}
+
+if (!shellCommandsAvailable()) {
+    cronJobStop("PHP on the command line cannot run git (exec is disabled), so the check cannot run\n");
+}
+
+$updates = checkForUpdates();
+
+/*
+ * Thrown rather than stopped: a fetch that fails is something to look at, and the dispatcher
+ * records a thrown message against the job so it shows on both Maintenance > Cron and the
+ * Update page. The last three lines, not the last one - git's final line is often the
+ * suggested fix rather than the problem.
+ */
+if ($updates->result !== 0) {
+    $update_check_error = trim(implode(' | ', array_slice($updates->output, -3)));
+    throw new Exception("git fetch failed: " . ($update_check_error === '' ? 'no output' : $update_check_error));
+}
+
+$update_check_latest = escapeSql($updates->latest_version);
+$update_check_commits = escapeSql((string) json_encode($updates->pending_commits));
+
+mysqli_query($mysqli, "UPDATE settings SET
+    config_update_latest_commit = '$update_check_latest',
+    config_update_pending_commits = '$update_check_commits',
+    config_update_checked_at = '" . date('Y-m-d H:i:s') . "'
+    WHERE company_id = 1");
+
+echo count($updates->pending_commits) . " commit(s) behind the remote\n";