Merge branch 'jc/retire-compaction-heuristics'

"git diff" and its family had two experimental heuristics to shift
the contents of a hunk to make the patch easier to read.  One of
them turns out to be better than the other, so leave only the
"--indent-heuristic" option and remove the other one.

* jc/retire-compaction-heuristics:
diff: retire "compaction" heuristics

diff --cc diff.c
Simple merge

diff --cc git-add--interactive.perl
Simple merge