[PATCH v5 0/7] Add --graft option to git replace

Here is a small patch series to implement:

        git replace [-f] --graft <commit> [<parent>...]

This patch series goes on top of the patch series that implements --edit.

The changes since v4, thanks to Junio and Peff, are:

- The series has been rebased on top of Peff's series
  to store the commit buffer length
  (jk/commit-buffer-length). This changes patch 1/7
  and fixes the problem that we lost everything after
  a NUL byte in the commit buffer. 

- Patches 5/7, 6/7 and 7/7 have been added to lose
  a gpg signature in the original commit buffer.
  
Notes:

- Maybe patches could be reordered or squashed, but
  I prefered not to do it in this round so that
  changes compared to previous version are easier to
  spot.

- Junio suggested to drop the merge-tag of a parent
  we are not going to keep, but to keep the merge-tag
  of a parent we are keeping. This has not yet been
  done. It is unfortunate that merge-tags don't use
  a format like the trailer format, because we could
  have factorised droping a merge-tag in the
  "git interpret-trailers" command.

Christian Couder (7):
  replace: add --graft option
  replace: add test for --graft
  Documentation: replace: add --graft option
  contrib: add convert-grafts-to-replace-refs.sh
  replace: refactor replacing parents
  replace: remove signature when using --graft
  replace: add test for --graft with signed commit

 Documentation/git-replace.txt             | 10 ++++
 builtin/replace.c                         | 79 ++++++++++++++++++++++++++++++-
 commit.c                                  | 34 +++++++++++++
 commit.h                                  |  2 +
 contrib/convert-grafts-to-replace-refs.sh | 28 +++++++++++
 t/t6050-replace.sh                        | 34 +++++++++++++
 6 files changed, 186 insertions(+), 1 deletion(-)
 create mode 100755 contrib/convert-grafts-to-replace-refs.sh