Merge branch 'mb/diff-default-to-indent-heuristics'

Merge branch 'mb/diff-default-to-indent-heuristics'

Make the "indent" heuristics the default in "diff" and diff.indentHeuristics
configuration variable an escape hatch for those who do no want it.

* mb/diff-default-to-indent-heuristics:
  add--interactive: drop diff.indentHeuristic handling
  diff: enable indent heuristic by default
  diff: have the diff-* builtins configure diff before initializing revisions
  diff: make the indent heuristic part of diff's basic configuration