Re: Bizarre missing changes (git bug?)

[Jeff King <peff@peff.net>]

On Tue, Jul 29, 2008 at 02:32:14PM +0200, Roman Zippel wrote:

> > Perhaps I am just slow, but I haven't been able to figure out what that
> > history is, or what the "correct" output should be. Can you try to state
> > more clearly what it is you are looking for?
> 
> Most frequently this involves changes where the same change is merged 
> twice. Another interesting example is kernel/printk.c where a change is 
> added and later removed again before it's merged.

I glanced briefly over "gitk kernel/printk.c" and it looks pretty sane.
I was really hoping for you to make your case as something like:

  1. here is an ascii diagram of an actual history graph (or a recipe of
     git commands for making one)
  2. here is what git-log (or gitk) produces for this history by
     default; and here is why it is not optimal (presumably some
     information it fails to convey)
  3. here is what git-log (or gitk) with --full-history produces; and
     here is why it is not optimal (presumably because it is too messy)
  4. here is what output I would like to see. Bonus points for "and here
     is an algorithm that accomplishes it."

> The point is now that I think the problem is solvable even within Linus' 
> constraints, so that git-log produces the right output by default and a 
> workaround like --full-history isn't needed anymore.

I think this is a separate issue. Even if you came up with some great
new history simplification, it likely wouldn't become the _default_
right away anyway. So you need to:

  1. produce a new simplification algorithm that is at least useful in
     _some_ contexts. Then this can be used when desired for those
     contexts. It almost doesn't matter how efficient it is, if it is
     providing results that are otherwise unavailable. A user can choose
     to take the performance hit to get those results.

  2. If that algorithm doesn't provide worse output in any other
     contexts _and_ it has similar performance to the current default,
     then it can be considered for the default.

But I haven't seen convincing evidence leading to step '1', so arguing
about step '2' seems pointless.

-Peff