Merge branch 'rs/xdiff-ignore-ws-w-func-context'

The "diff" machinery learned not to lose added/removed blank lines
in the context when --ignore-blank-lines and --function-context are
used at the same time.

* rs/xdiff-ignore-ws-w-func-context:
  xdiff: unignore changes in function context

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