Re: Editing the root commit

[Chris Webb <chris@arachsys.com>]

Junio C Hamano <gitster@pobox.com> 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.