Merge branch 'ja/git-diff-doc-markup'

Documentation mark-up updates.

* ja/git-diff-doc-markup:
  doc: git-diff: apply format changes to config part
  doc: git-diff: apply format changes to diff-generate-patch
  doc: git-diff: apply format changes to diff-format
  doc: git-diff: apply format changes to diff-options
  doc: git-diff: apply new documentation guidelines