Merge branch 'pw/diff-color-moved-fix' into seen

Merge branch 'pw/diff-color-moved-fix' into seen

Long-overdue correctness and performance update to "diff
--color-moved" feature.

* pw/diff-color-moved-fix:
  diff --color-moved: intern strings
  diff --color-moved-ws=allow-indentation-change: improve hash lookups
  diff --color-moved: stop clearing potential moved blocks
  diff --color-moved: shrink potential moved blocks as we go
  diff --color-moved: unify moved block growth functions
  diff --color-moved: call comparison function directly
  diff --color-moved-ws=allow-indentation-change: simplify and optimize
  diff: simplify allow-indentation-change delta calculation
  diff --color-moved: avoid false short line matches and bad zebra coloring
  diff --color-moved=zebra: fix alternate coloring