Merge branch 'pw/add-p-recount' into pu

Merge branch 'pw/add-p-recount' into pu

"git add -p" has been lazy in coalescing split patches before
passing the result to underlying "git apply", leading to corner
case bugs; the logic to prepare the patch to be applied after hunk
selections has been tightened.

* pw/add-p-recount:
  add -p: don't rely on apply's '--recount' option
  add -p: fix counting when splitting and coalescing
  add -p: calculate offset delta for edited patches
  add -p: adjust offsets of subsequent hunks when one is skipped
  t3701: add failing test for pathological context lines
  t3701: don't hard code sha1 hash values
  t3701: use test_write_lines and write_script
  t3701: indent here documents
  add -i: add function to format hunk header