Merge branch 'pw/add-patch-with-suppress-blank-empty'

"git add -p" by users with diff.suppressBlankEmpty set to true
failed to parse the patch that represents an unmodified empty line
with an empty line (not a line with a single space on it), which
has been corrected.

* pw/add-patch-with-suppress-blank-empty:
  add-patch: use normalize_marker() when recounting edited hunk
  add-patch: handle splitting hunks with diff.suppressBlankEmpty

diff --cc add-patch.c
Simple merge

diff --cc t/t3701-add-interactive.sh
Simple merge