From https://secure.phabricator.com/conpherence/1336/#16787, if an imported workspace finds an empty dir where the workdir should be, it doesn't recover.
```
$ '/home/avive/devtools/phabricator/bin/repository' update -- LST
[2015-11-08 15:10:25] EXCEPTION: (CommandException) Command failed with error #128!
COMMAND
git remote show -n origin
STDOUT
(empty)
STDERR
fatal: Not a git repository (or any of the parent directories): .git
at [<phutil>/src/future/exec/ExecFuture.php:416]
arcanist(head=master, ref.master=2db40f995337, custom=1), phabricator(head=master, ref.master=a2f909f0bd0a), phutil(head=master, ref.master=610ca9eba906)
#0 ExecFuture::resolvex() called at [<phabricator>/src/applications/repository/storage/PhabricatorRepository.php:346]
#1 PhabricatorRepository::execxLocalCommand(string) called at [<phabricator>/src/applications/repository/engine/PhabricatorRepositoryEngine.php:66]
#2 PhabricatorRepositoryEngine::verifyGitOrigin(PhabricatorRepository) called at [<phabricator>/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php:92]
#3 PhabricatorRepositoryPullEngine::pullRepository() called at [<phabricator>/src/applications/repository/management/PhabricatorRepositoryManagementUpdateWorkflow.php:80]
#4 PhabricatorRepositoryManagementUpdateWorkflow::execute(PhutilArgumentParser) called at [<phutil>/src/parser/argument/PhutilArgumentParser.php:406]
#5 PhutilArgumentParser::parseWorkflowsFull(array) called at [<phutil>/src/parser/argument/PhutilArgumentParser.php:301]
#6 PhutilArgumentParser::parseWorkflows(array) called at [<phabricator>/scripts/repository/manage_repositories.php:22]
```
This also fails for //hosted// repos, but in the case of imported ones we can actually recover (By deleting whatever we find there. We do that for other failed cases).