Merge branch 'en/fill-directory-fixes'

Merge branch 'en/fill-directory-fixes'

Assorted fixes to the directory traversal API.

* en/fill-directory-fixes:
  dir.c: use st_add3() for allocation size
  dir: consolidate similar code in treat_directory()
  dir: synchronize treat_leading_path() and read_directory_recursive()
  dir: fix checks on common prefix directory
  dir: break part of read_directory_recursive() out for reuse
  dir: exit before wildcard fall-through if there is no wildcard
  dir: remove stray quote character in comment
  Revert "dir.c: make 'git-status --ignored' work within leading directories"
  t3011: demonstrate directory traversal failures