Merge branch 'maint'

Merge branch 'maint'

* maint:
  pull: do not display fetch usage on --help-all
  git-tag.txt: list all modes in the description
  commit,status: describe -u likewise
  add: describe --patch like checkout, reset
  commit,merge,tag: describe -m likewise
  clone,init: describe --template using the same wording
  commit,status: describe --porcelain just like push
  commit,tag: use same wording for -F
  configure: use AC_LANG_PROGRAM consistently
  string_list_append: always set util pointer to NULL
  correct type of EMPTY_TREE_SHA1_BIN