[PATCH v3 0/4] use the pager in 'add -p'

This iterations fixes this error:

t3701-add-interactive.sh:619: error: head -c is not portable (use test_copy_bytes BYTES <file >out): test_write_lines P q | GIT_PAGER="head -c 1" test_terminal git add -p >actual gmake[1]: *** [Makefile:132: test-lint-shell-syntax] Error 1

Rubén Justo (4):
  add-patch: test for 'p' command
  pager: do not close fd 2 unnecessarily
  pager: introduce wait_for_pager
  add-patch: render hunks through the pager

 add-patch.c                | 18 ++++++++++++---
 pager.c                    | 45 +++++++++++++++++++++++++++++++++-----
 pager.h                    |  1 +
 t/t3701-add-interactive.sh | 44 +++++++++++++++++++++++++++++++++++++
 4 files changed, 100 insertions(+), 8 deletions(-)

Range-diff against v3:
-:  ---------- > 1:  6b37507ddd add-patch: test for 'p' command
-:  ---------- > 2:  5497fa020b pager: do not close fd 2 unnecessarily
-:  ---------- > 3:  30e772cf7c pager: introduce wait_for_pager
1:  f7cb00b654 ! 4:  913e7f3d09 add-patch: render hunks through the pager
    @@ t/t3701-add-interactive.sh: test_expect_success 'print again the hunk' '
     +
     +test_expect_success TTY 'P does not break if pager ends unexpectedly' '
     +	test_when_finished "rm -f huge_file; git reset" &&
    -+	printf "%2500000s" Y >huge_file &&
    ++	printf "\n%2500000s" Y >huge_file &&
     +	git add -N huge_file &&
    -+	test_write_lines P q | GIT_PAGER="head -c 1" test_terminal git add -p >actual
    ++	test_write_lines P q | GIT_PAGER="head -n 1" test_terminal git add -p >actual
     +'
     +
      test_expect_success 'split hunk "add -p (edit)"' '