force push, fatal: '.git/tmp/subrepo/ddl' is a missing but already registered worktree

[jcalfee]

What does missing but already registered mean?

$ git subrepo push ddl --force
git-subrepo: Command failed: 'git worktree add .git/tmp/subrepo/ddl subrepo/ddl'.
fatal: '.git/tmp/subrepo/ddl' is a missing but already registered worktree;
use 'add -f' to override, or 'prune' or 'remove' to clear
Preparing worktree (checking out 'subrepo/ddl')

[jcalfee]

$ git subrepo help prune
No help found for 'prune'

$ git subrepo help remove
No help found for 'remove'

$ git subrepo help add
No help found for 'add'

$ git subrepo help push|egrep "prune|remove|add"
<<empty>>

[jcalfee]

I did this with subtree directly instead like this: https://stackoverflow.com/a/33178233/766233 so I can't really test commands anymore. Just close if you like. Please let me know if there is something simple you see that I may have messed up in my subrepo environment. Thank you!