Re: [PATCH v4 07/12] rebase: add --update-refs option

> From: Derrick Stolee <derrickstolee@github.com>
> 
> When working on a large feature, it can be helpful to break that feature
> into multiple smaller parts that become reviewed in sequence. During
> development or during review, a change to one part of the feature could
> affect multiple of these parts. An interactive rebase can help adjust
> the multi-part "story" of the branch.
> 
> However, if there are branches tracking the different parts of the
> feature, then rebasing the entire list of commits can create commits not
> reachable from those "sub branches". It can take a manual step to update
> those branches.
> 
> Add a new --update-refs option to 'git rebase -i' that adds 'update-ref
> <ref>' steps to the todo file whenever a commit that is being rebased is
> decorated with that <ref>. At the very end, the rebase process updates
> all of the listed refs to the values stored during the rebase operation.
> 
> Be sure to iterate after any squashing or fixups are placed. Update the
> branch only after those squashes and fixups are complete. This allows a
> --fixup commit at the tip of the feature to apply correctly to the sub
> branch, even if it is fixing up the most-recent commit in that part.
> 
> One potential problem here is that refs decorating commits that are
> already marked as "fixup!" or "squash!" will not be included in this
> list. Generally, the reordering of the "fixup!" and "squash!" is likely
> to change the relative order of these refs, so it is not recommended.
> The workflow here is intended to allow these kinds of commits at the tip
> of the rebased branch while the other sub branches come along for the
> ride without intervention.
> 
> This change update the documentation and builtin to accept the
> --update-refs option as well as updating the todo file with the
> 'update-ref' commands. Tests are added to ensure that these todo
> commands are added in the correct locations.
> 
> This change does _not_ include the actual behavior of tracking the
> updated refs and writing the new ref values at the end of the rebase
> process. That is deferred to a later change.
> 
> Signed-off-by: Derrick Stolee <derrickstolee@github.com>
> ---
>  Documentation/git-rebase.txt  |   8 +++
>  builtin/rebase.c              |   5 ++
>  sequencer.c                   | 107 ++++++++++++++++++++++++++++++++++
>  sequencer.h                   |   1 +
>  t/t2407-worktree-heads.sh     |  22 +++++++
>  t/t3404-rebase-interactive.sh |  70 ++++++++++++++++++++++
>  6 files changed, 213 insertions(+)
> 
> diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
> index 262fb01aec0..e7611b4089c 100644
> --- a/Documentation/git-rebase.txt
> +++ b/Documentation/git-rebase.txt
> @@ -609,6 +609,13 @@ provided. Otherwise an explicit `--no-reschedule-failed-exec` at the
>  start would be overridden by the presence of
>  `rebase.rescheduleFailedExec=true` configuration.
>  
> +--update-refs::

> +	are being rebased. Any branches that are checked out in a worktree
> +	or point to a `squash! ...` or `fixup! ...` commit are not updated
> +	in this way.
> +
>  INCOMPATIBLE OPTIONS
>  --------------------
>  

> @@ -1124,6 +1126,9 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>  		OPT_BOOL(0, "autosquash", &options.autosquash,
>  			 N_("move commits that begin with "
>  			    "squash!/fixup! under -i")),
> +		OPT_BOOL(0, "update-refs", &options.update_refs,
> +			 N_("update local refs that point to commits "