Re: [BUG] - git rebase -i performs rebase when it shouldn't?

From: Jeff King <peff@peff.net>
Date: Apr 10, 2010, 04:26 UTC
Message-ID: <20100410042609.GA24295@coredump.intra.peff.net>
In-Reply-To: <z2q76c5b8581004091235ucd9b2a52i223b3191b288c42a@mail.gmail.com>

On Fri, Apr 09, 2010 at 03:35:42PM -0400, Eugene Sajine wrote:

Show 15 quoted lines

> In case of this situation
> 
>        A  master
>         \
>          B  next
>           \
>            C  topic
> 
> 
> $ git rebase --onto master topic
> First, rewinding head to replay your work on top of it...
> fatal: Not a range.
> Nothing to do.
> 
> Which is OK.

I think this doesn't do quite what you thought. It's true there is "nothing to do" as in "nothing to apply", but it _did_ in fact rewind topic back to "master".

You seem to be thinking that

  git rebase --onto master topic

means "rebase everything from master to topic onto master". It doesn't. That would be:

  git rebase master topic

or, if you are already on topic, just

  git rebase master

The "--onto" option takes an argument, which says "put the commits on top of here, even though it was not the upstream base otherwise specified". So what your command does is say "using the current branch (which is topic), take everything built on top of topic (which is nothing), and rebuild it on top of master".

So no, it's not a bug. Yes, it's a terrible interface. There is really no reason IMHO for rebase to take a "which branch to operate on" argument at all. It should just operate on HEAD, like merge does. If you want to merge on a different branch, you "git checkout" that branch first.

That would have made your error less likely, because you would have had no reason to think you needed to say "topic" at all.

-Peff