Merge tag 'v2.25.0-rc0' into git-po-master

Git 2.25-rc0

* tag 'v2.25.0-rc0': (531 commits)
  Git 2.25-rc0
  sparse-checkout: improve OS ls compatibility
  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
  t4015: improve coverage of function context test
  commit: forbid --pathspec-from-file --all
  t3434: mark successful test as such
  notes.h: fix typos in comment
  t6030: don't create unused file
  t5580: don't create unused file
  t3501: don't create unused file
  bisect--helper: convert `*_warning` char pointers to char arrays.
  The sixth batch
  fix-typo: consecutive-word duplications
  Makefile: drop GEN_HDRS
  built-in add -p: show helpful hint when nothing can be staged
  built-in add -p: only show the applicable parts of the help text
  built-in add -p: implement the 'q' ("quit") command
  ...