Truncate logSource in Harbormaster to the database column limit

Summary: This can be a command, which might be arbitrarily long, but the column is VARCHAR(255).

Test Plan: `grep`

Reviewers: dctrwatson, btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D8446

src/applications/harbormaster/storage/build/HarbormasterBuild.php

@@ -113,6 +113,8 @@ final class HarbormasterBuild extends HarbormasterDAO
     $log_source,
     $log_type) {
 
+    $log_source = phutil_utf8_shorten($log_source, 250);
+
     $log = HarbormasterBuildLog::initializeNewBuildLog($build_target)
       ->setLogSource($log_source)
       ->setLogType($log_type)