Bug with arcanist when running "arc diff" without an active branch. Trace:
>>> [50] (+9,233) <exec> $ git symbolic-ref --quiet HEAD <<< [50] (+9,235) <exec> 1,791 us [2023-05-22 10:35:55] EXCEPTION: (RuntimeException) strlen(): Passing null to parameter #1 ($string) of type string is deprecated at [<arcanist>/src/error/PhutilErrorHandler.php:261] arcanist(), tmphutil() #0 PhutilErrorHandler::handleError(integer, string, string, integer) called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:2484] #1 ArcanistDiffWorkflow::getDiffOntoTargets() called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:2462] #2 ArcanistDiffWorkflow::updateOntoDiffProperty() called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:435] #3 ArcanistDiffWorkflow::run() called at [<arcanist>/scripts/arcanist.php:427] <<< [1] (+9,273) <exec> 9,273,390 us
I've found a fix in the phabricator repo and I think the same should be applied here: https://secure.phabricator.com/rARCc39ab20eb3717a15aed2467842bd77d9addce96a