Merge branch 'ps/completion-with-reftable-fix'

Completion update to prepare for reftable

* ps/completion-with-reftable-fix:
  completion: treat dangling symrefs as existing pseudorefs
  completion: silence pseudoref existence check
  completion: improve existence check for pseudo-refs
  t9902: verify that completion does not print anything
  completion: discover repo path in `__git_pseudoref_exists ()`