Merge branch 'maint'

Merge branch 'maint'

* maint:
  push: point to 'git pull' and 'git push --force' in case of non-fast forward
  Documentation: add: <filepattern>... is optional
  Change mentions of "git programs" to "git commands"
  Documentation: merge: one <remote> is required
  help.c: give correct structure's size to memset()