[RFC/PATCH 00/18] WIP implement cherry-pick/revert --continue

This a a work in progress to show where this is going and to discuss it.

There are many things missing among other:

 * no documentation
 * missing tests, especially for "revert"
 * when cherry-pick fails the error message does not advertise --continue
 * resolving a failing cherry-pick is not handled
 * commit messages could be improved a lot
 * ...

Many patches in this series are replacing calls to "die()" by "return error()", because the TODO and DONE files are written only when cherry-pick fails. This is efficient but perhaps it would be simpler and safer to write them before each cherry-pick just in case it fails, so that the "die()" calls don't need to be removed.

Christian Couder (17):
  advice: add error_resolve_conflict() function
  revert: change many die() calls into "return error()" calls
  usage: implement error_errno() the same way as die_errno()
  revert: don't die when write_message() fails
  commit: move reverse_commit_list() into commit.{h,c}
  revert: remove "commit" global variable
  revert: put option information in an option struct
  revert: refactor code into a new pick_commits() function
  revert: make pick_commits() return an error on --ff incompatible
    option
  revert: make read_and_refresh_cache() and prepare_revs() return
    errors
  revert: add get_todo_content() and create_todo_file()
  revert: write TODO and DONE files in case of failure
  revert: add option parsing for option --continue
  revert: move global variable "me" into "struct args_info"
  revert: add NONE action and make parse_args() manage it
  revert: add remaining instructions in todo file
  revert: implement --continue processing

Stephan Beyer (1):
  revert: implement parsing TODO and DONE files

 advice.c                            |   25 +-
 advice.h                            |    1 +
 builtin/revert.c                    |  692 ++++++++++++++++++++++++++++-------
 commit.c                            |   11 +
 commit.h                            |    2 +
 git-compat-util.h                   |    1 +
 merge-recursive.c                   |   11 -
 t/t3508-cherry-pick-many-commits.sh |  101 +++++
 usage.c                             |   28 ++-
 9 files changed, 717 insertions(+), 155 deletions(-)