Merge branch 'es/format-patch-rangediff'

"git format-patch" learned a new "--range-diff" option to explain the difference between this version and the previous attempt in the cover letter (or after the tree-dashes as a comment). * es/format-patch-rangediff: format-patch: allow --range-diff to apply to a lone-patch format-patch: add --creation-factor tweak for --range-diff format-patch: teach --range-diff to respect -v/--reroll-count format-patch: extend --range-diff to accept revision range format-patch: add --range-diff option to embed diff in cover letter range-diff: relieve callers of low-level configuration burden range-diff: publish default creation factor range-diff: respect diff_option.file rather than assuming 'stdout'