[PATCH v3 0/4] rebase -i: mark commits that begin empty in todo editor

Changes since v2:

 * Addressed feedback from Junio in patch 2, including moving some of the
   wording to the new patch (see next point)
 * Edited jt/rebase-allow-duplicate to include the changes Jonathan
   mentioned on the list, then rebased it on top of this series, and made
   the related options mention each other.

Elijah Newren (3):
  rebase -i: mark commits that begin empty in todo editor
  rebase: reinstate --no-keep-empty
  rebase: fix an incompatible-options error message

Jonathan Tan (1):
  rebase --merge: optionally skip upstreamed commits

 Documentation/git-rebase.txt      | 70 +++++++++++++++++++++-------
 builtin/rebase.c                  | 24 +++++++---
 sequencer.c                       | 14 +++++-
 sequencer.h                       |  4 +-
 t/t3402-rebase-merge.sh           | 77 +++++++++++++++++++++++++++++++
 t/t3421-rebase-topology-linear.sh | 10 ++--
 t/t3424-rebase-empty.sh           | 36 +++++++++++++++
 7 files changed, 202 insertions(+), 33 deletions(-)

base-commit: 274b9cc25322d9ee79aa8e6d4e86f0ffe5ced925
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-757%2Fnewren%2Frebase-mark-empty-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-757/newren/rebase-mark-empty-v3
Pull-Request: https://github.com/git/git/pull/757

Range-diff vs v2:

 1:  0d94eea376a = 1:  0d94eea376a rebase -i: mark commits that begin empty in todo editor
 2:  e15c599c874 ! 2:  3a5bedc68d6 rebase: reinstate --no-keep-empty
     @@ Commit message
      
          Commit d48e5e21da ("rebase (interactive-backend): make --keep-empty the
          default", 2020-02-15) turned --keep-empty (for keeping commits which
     -    start empty) into the default.  That commit viewed this, though as
     -    turning that flag into a no-op.  As such, --no-keep-empty was translated
     -    into undoing a no-op, i.e. also a no-op.  The logic underpinning that
     -    commit was:
     +    start empty) into the default.  The logic underpinning that commit was:
      
            1) 'git commit' errors out on the creation of empty commits without an
               override flag
     @@ Commit message
          look really weird despite making perfect sense (the first will drop
          commits which become empty, but keep commits that started empty; the
          second will keep commits which become empty, but drop commits which
     -    started empty).
     +    started empty).  However, --no-keep-empty was named years ago and we are
     +    predominantly keeping it for backward compatibility; also we suspect it
     +    will only be used rarely since folks already have a simple way to drop
     +    commits they don't want with an interactive rebase.
      
          Reported-by: Bryan Turner <bturner@atlassian.com>
          Reported-by: Sami Boukortt <sami@boukortt.com>
     @@ Documentation/git-rebase.txt: See also INCOMPATIBLE OPTIONS below.
      -always dropped.
      +Note that commits which start empty are kept (unless --no-keep-empty
      +is specified), and commits which are clean cherry-picks (as determined
     -+by `git log --cherry-mark ...`) are detected and dropped as a preliminary
     -+step (unless --keep-cherry-picks is passed).
     ++by `git log --cherry-mark ...`) are always dropped.
       +
       See also INCOMPATIBLE OPTIONS below.
       
     @@ Documentation/git-rebase.txt: See also INCOMPATIBLE OPTIONS below.
      -	to halt.
      +	Do not keep commits that start empty before the rebase
      +	(i.e. that do not change anything from its parent) in the
     -+	result.  For commits which become empty after rebasing, see
     -+	the --empty and --keep-cherry-pick flags.
     ++	result.  The default is to keep commits which start empty,
     ++	since creating such commits requires passing the --allow-empty
     ++	override flag to `git commit`, signifying that a user is very
     ++	intentionally creating such a commit and thus wants to keep
     ++	it.
       +
      -See also BEHAVIORAL DIFFERENCES and INCOMPATIBLE OPTIONS below.
     ++Usage of this flag will probably be rare, since you can get rid of
     ++commits that start empty by just firing up an interactive rebase and
     ++removing the lines corresponding to the commits you don't want.  This
     ++flag exists as a convenient shortcut, such as for cases where external
     ++tools generate many empty commits and you want them all removed.
     +++
     ++For commits which do not start empty but become empty after rebasing,
     ++see the --empty flag.
     +++
      +See also INCOMPATIBLE OPTIONS below.
       
       --allow-empty-message::
 3:  ee5e42361fc = 3:  5c8863b9d34 rebase: fix an incompatible-options error message
 -:  ----------- > 4:  20d3a50f5a4 rebase --merge: optionally skip upstreamed commits