Re: [PATCH 2/2] repack -ad: prune the list of shallow commits

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

Hi Junio,

On Tue, 17 Jul 2018, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > I'm OK with having a partial fix, or one that fixes immediate pain
> > without doing a big cleanup, as long as it doesn't make anything _worse_
> > in a user-visible way. And that's really my question: is pruning here
> > going to bite people unexpectedly (not rhetorical -- I really don't
> > know)?
> 
> Yeah, that matches the general guideline I follow when reviewing a
> patch that claims to make existing things better.  And I do not
> think I can explain to a third person why pruning here is a good
> idea and won't cause problems, after seeing these patches and
> the discussion from the sideline.

It is very easy to explain: `git repack` can drop unreachable commits
without further warning, making the corresponding entries in
`.git/shallow` invalid, which causes serious problems when deepening the
branches.

The solution is easy: drop also the now-invalid entries in `.git/shallow`
after dropping unreachable commits unceremoniously.

While I am sympathetic to Peff's attempt to make this a bit more general,
I think he overthinks it, and we do not even need to complexify the code
for now.

Ciao,
Dscho