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Once upon a time, I dreamt of an interactive rebase that would not
flatten branch structure, but instead recreate the commit topology

My original attempt was --preserve-merges, but that design was so
limited that I did not even enable it in interactive mode.

Subsequently, it *was* enabled in interactive mode, with the predictable
consequences: as the --preserve-merges design does not allow for
specifying the parents of merge commits explicitly, all the new commits'
parents are defined *implicitly* by the previous commit history, and
hence it is *not possible to even reorder commits*.

This design flaw cannot be fixed. Not without a complete re-design, at
least. This patch series offers such a re-design.

Think of --recreate-merges as "--preserve-merges done right". It
introduces new verbs for the todo list, `label`, `reset` and `merge`.
For a commit topology like this:

            A - B - C
              \   /

the generated todo list would look like this:

            # branch D
            pick 0123 A
            label branch-point
            pick 1234 D
            label D

            reset branch-point
            pick 2345 B
            merge -C 3456 D # C

There are more patches in the pipeline, based on this patch series, but
left for later in the interest of reviewable patch series: one mini
series to use the sequencer even for `git rebase -i --root`, and another
one to add support for octopus merges to --recreate-merges.

Changes since v2:

- fixed the incorrect comment for rebase_path_refs_to_delete.

- we now error out properly if read_cache_unmerged() fails.

- if there are unresolved merge conflicts, the `reset` command now errors out
  (even if the current design should not allow for such a scenario to occur).

- a diff hunk that was necessary to support `bud` was dropped from 2/10.

- changed all `rollback_lock_file(); return error_errno(...);` patterns to
  first show the errors (i.e. using the correct errno). This added 1/11.

- The temporary refs are now also cleaned up upon `git rebase --abort`.

- Reworked the entire patch series to support

	merge -C <commit> <tip> # <oneline>

  instead of the previous `merge <commit> <tip> <oneline>`.

- Dropped the octopus part of the description of the `merge` command in
  the usage at the bottom of the todo list, as it is subject to change.

- The autosquash handling was not elegant, and cuddled into the same
  commit as the post-rewrite changes. Now, the autosquash handling is a
  lot more elegant, and a separate introductory patch (as it arguably
  improves the current code on its own).

Johannes Schindelin (11):
  sequencer: avoid using errno clobbered by rollback_lock_file()
  sequencer: make rearrange_squash() a bit more obvious
  sequencer: introduce new commands to reset the revision
  sequencer: introduce the `merge` command
  sequencer: fast-forward merge commits, if possible
  rebase-helper --make-script: introduce a flag to recreate merges
  rebase: introduce the --recreate-merges option
  sequencer: make refs generated by the `label` command worktree-local
  sequencer: handle post-rewrite for merge commands
  pull: accept --rebase=recreate to recreate the branch topology
  rebase -i: introduce --recreate-merges=[no-]rebase-cousins

Stefan Beller (1):
  git-rebase--interactive: clarify arguments

 Documentation/config.txt               |   8 +
 Documentation/git-pull.txt             |   5 +-
 Documentation/git-rebase.txt           |  14 +-
 builtin/pull.c                         |  14 +-
 builtin/rebase--helper.c               |  13 +-
 builtin/remote.c                       |   2 +
 contrib/completion/git-completion.bash |   4 +-             |  22 +-                          |  16 +
 refs.c                                 |   3 +-
 sequencer.c                            | 736 ++++++++++++++++++++++++++++++++-
 sequencer.h                            |   7 +
 t/      | 208 ++++++++++
 13 files changed, 1021 insertions(+), 31 deletions(-)
 create mode 100755 t/

base-commit: 5be1f00a9a701532232f57958efab4be8c959a29

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