Merge branch 'maint'

* maint:
  git-svn: understand grafts when doing dcommit
  git-diff: don't squelch the new SHA1 in submodule diffs
  git-svn: fix "Malformed network data" with svn:// servers
  (cvs|svn)import: Ask git-tag to overwrite old tags.
  Documentation / grammer nit