Re: Editing the root commit

Junio C Hamano [off-list ref] writes:

What if we do not say --onto here?  I am not asking what the current
implementation does (we get an error message saying "I want 'onto'
specified").  What _should_ this command mean to a na??ve user?

    $ git rebase [-i] --root

I think it should mean "replay all my history down to root".  The
original root commit should become the new root commit in the
rewritten history.

Yes, I definitely agree with everything you say here. That's exactly what
I'd expect from git rebase --root without --onto, and what I'd hope to be
able to implement in a patch series.

For the root commit in the history, you check it out on the detached
HEAD.  Under "--interactive" if the insn sheet tells you to allow
the user to "edit/amend/reword" it, give control back the user after
you have detached HEAD at that commit.  The user experience should
be identical to the case you are replaying on an existing commit
after that point.

I think it might a little more complicated than detecting when we have to do
a commit --amend on the root commit though? The user might have reordered
the first commit (introducing A and B, say) with the second commit
(introducing C and D), or dropped the original root commit entirely.

My understanding of the way --interactive works at the moment is that it
checks out the starting commit (whether given explicitly by --onto or taken
from <upstream>) and then 'plays out' the commits as described in the
instruction sheet.

I could re-use this unchanged if I could do a git checkout --orphan without
having to create a new branch, but I don't think this is allowed: I can have
a detached head or make an orphan checkout onto a new branch, but not both
at the same time? Would you prefer that I create a temporary branch just to
be able to git checkout --orphan onto it here, or that I add support for
this kind of 'detached HEAD with no parent' state, or is there a natural way
to rework --interactive without needing to do this which I'm missing?

Best wishes,

Chris.