Manipulating existing revisions by push or pull?

Manipulating existing revisions by push or pull?

[Lasse Kliemann]

I've got a conceptual question.

I know that one can change history in a local repository with the 
'rebase' command, e.g., using the interactive mode. 

Is there any way to modify existing revisions in a local 
repository by a pull (and merge, whatever) from a remote one? Or 
is there any way to modify existing revisions in a remote 
repository by a push (or whatever) from a local one?

Put a different way: consider there is a hostile entity from 
which I pull or which I allow to push to me. Can this entity 
fiddle with my history? Can it change the data in existing 
revisions in my repository? Or can it only make new revisions 
grow on my side?

Thank you
Lasse

Re: Manipulating existing revisions by push or pull?

[Junio C Hamano]

"Lasse Kliemann" <lasse-gmane-git-2009@mail.plastictree.net> writes:

> Put a different way: consider there is a hostile entity from 
> which I pull or which I allow to push to me. Can this entity 
> fiddle with my history? Can it change the data in existing 
> revisions in my repository? Or can it only make new revisions 
> grow on my side?

If you allow your ref to get updated to an arbitrary value, you are lost,
unless you have signed tags that anchor things in place, in which case you
can trust the part of history that is reachable from them.