Re: [PATCH/RFC] filter-branch: support skipping of commits more easily

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Fri, 7 Jun 2007, linux@horizon.com wrote:

> > I think that is fine; in effect, by saying "skip" B, you are
> > squashing B-C into C'.
> > 
> > Does this mean that, given
> > 
> >           C---D---E
> >          /   /
> >         A---B
> > 
> > and if commit-filter says "skip" on D, the written history would
> > look like this?
> > 
> >           C'------E'
> >          /       /
> >         A'--B'--'
> > 
> > The new commit E' would become an evil merge that has difference
> > between D and E in the original history?
> > 
> > I am not objecting; just trying to get a mental picture.
> 
> I think, for compatibility with the existing git path limiter,
> it should delete D from the history only if:
> 1) Told to skip D, and
> 2) Told to skip B or C (or both).
> 
> So you could get A--B--E' or A--C--E' or even A--E', but D would only
> be deleted if it wasn't needed as a merge marker.
> 
> That's probably a little more complex to implement, but it feels like
> The Right Thing.

... but if that script should do that, the name "filter"-branch was a 
misnomer.

It filters the _branch_. In the sense that a branch is one or more perls 
of commits, uniting in the tip of that branch.

If you want to skip a commit, that is fine. But a commit is _not_ a patch, 
no sir. It is a revision.

The fact that we actually are able to extract nice patches from any patch 
series, does not mean that the revisions are actually only deltas with 
regard to the previous commit. To the contrary: we actually allow -- and 
encourage -- git-diff between different revisions, be they on the same 
branch or not. That alone should tell everybody that a revision is a 
revision is a revision, and _not_ a delta.

So, when you filter commits, you should not expect a certain _patch_ to be 
skipped when you say "skip" (or maybe "squash", which I actually like 
better, because it is as unambiguous as you get it), but a _commit_ (AKA 
revision) to be skipped.

Ciao,
Dscho