Merge branch 'maint'

* maint:
  git-format-patch --in-reply-to: accept <message@id> with angle brackets
  git-add -u: do not barf on type changes
  Remove duplicate note about removing commits with git-filter-branch
  git-clone: improve error message if curl program is missing or not executable
  hooks--update: Explicitly check for all zeros for a deleted ref.