[GSoC] [PATCH 00/18] builtin rebase options

This patch series completes the support for all rebase options in the builtin rebase. This converts the remaining command-line options.

The previous patch series taught the builtin rebase to handle different actions, this patch series will continue adding functionality to builtin rebase by teaching it to handle options handled by original rebase i.e. `--signoff`, `rerere-autoupdate`, et al.

It adds the functionality to the previous patch series, (https://public-inbox.org/git/20180808150622.9614-1-predatoramigo@gmail.com).

This is the fourth patch series that brings us more closer to a builtin "git rebase".

If you like to view the development branch, you can view (https://github.com/git/git/pull/505), where I have kept my commits up to date and leveraged Travis(there is sporadic failures in t5520 for macos gcc and isn't due to my patches) for extra testing other than my system.

The next in line patch series which I'll be sending out today are:

builtin rebase rest: The builtin rebase will convert all the remaining shell scripts from the original rebase to C. default to builtin rebase: This will turn on the feature-complete builtin rebase to on.

These patch series are built on top of each other, i.e. they depend on this order.

Pratik Karki (18):
  builtin rebase: allow selecting the rebase "backend"
  builtin rebase: support --signoff
  builtin rebase: support --rerere-autoupdate
  builtin rebase: support --committer-date-is-author-date
  builtin rebase: support `ignore-whitespace` option
  builtin rebase: support `ignore-date` option
  builtin rebase: support `keep-empty` option
  builtin rebase: support `--autosquash`
  builtin rebase: support `--gpg-sign` option
  builtin rebase: support `-C` and `--whitespace=<type>`
  builtin rebase: support `--autostash` option
  builtin rebase: support `--exec`
  builtin rebase: support `--allow-empty-message` option
  builtin rebase: support --rebase-merges[=[no-]rebase-cousins]
  merge-base --fork-point: extract libified function
  builtin rebase: support `fork-point` option
  builtin rebase: add support for custom merge strategies
  builtin rebase: support --root

 builtin/merge-base.c |  81 +-------
 builtin/rebase.c     | 449 ++++++++++++++++++++++++++++++++++++++++++-
 commit.c             |  81 ++++++++
 commit.h             |   2 +
 4 files changed, 528 insertions(+), 85 deletions(-)