Merge branch 'maint'

* maint:
  Amend git-push refspec documentation
  git-gc --prune is deprecated
  svn-git: Use binmode for reading/writing binary rev maps
  diff options documentation: refer to --diff-filter in --name-status
  Don't force imap.host to be set when imap.tunnel is set
  git-clone.txt: Adjust note to --shared for new pruning behavior of git-gc
  git-svn bug with blank commits and author file
  archive.c: format_subst - fixed bogus argument to memchr
  copy.c: copy_fd - correctly report write errors
  gitattributes: Fix subdirectory attributes specified from root directory