Merge branch 'master-for-junio' of git://repo.or.cz/git/fastimport; branch 'maint'

Merge branch 'master-for-junio' of git://repo.or.cz/git/fastimport; branch 'maint'

* 'master-for-junio' of git://repo.or.cz/git/fastimport:
  fast-import: Fail if a non-existant commit is used for merge
  fast-import: Avoid infinite loop after reset

* maint:
  Fix diff-options references in git-diff and git-format-patch
  Add definition of <commit-ish> to the main git man page.
  Begin SubmittingPatches with a check list
  fast-import: Fail if a non-existant commit is used for merge
  fast-import: Avoid infinite loop after reset