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'