Merge branch 'sb/diff-color-move'

A recently added "--color-moved" feature of "diff" fell into
infinite loop when ignoring whitespace changes, which has been
fixed.

* sb/diff-color-move:
  diff: fix infinite loop with --color-moved --ignore-space-change

diff --cc diff.c
Simple merge

diff --cc t/t4015-diff-whitespace.sh
Simple merge