A tale of user-friendliness with "hg merge" and "hg rollback".

[Rob Landley]

On Monday 12 October 2009 15:32:00 Benoit Boissinot wrote:
> On Mon, Oct 12, 2009 at 10:06 PM, Rob Landley <rob at landley.net> wrote:
> > I've been maintaining a little project in mercurial for a few years now,
> > but I always had people send me patches instead of doing pulls and
> > dealing with branches.
> >
> > [snip]
> >
> > So now I just want to just get the repository back to a state where I
> > understood it, so I do an "hg rollback".  Hoping this would not only kick
> > out this weird abstract uncommitted merge object, but maybe even remove
> > the one commit I'd pulled from Mark that was hiding all my recent work,
> > which was showing up as "tip".
> >
> > Except that doing this seems to have destroyed the entire repository.
> >  After the rollback, the entire repository was... gone.  "hg log -v"
> > listed nothing. "hg branches" listed nothing.  Even giving it explicit
> > revision numbers well back in the history ("hg log -r 800") produced
> > _nothing_.
>
> Every revlog from the repo disappeared, the repo is basically empty now.
> Any other hint to help us understand what might have happened (FS, OS,
> etc.) ?

Ubuntu 9.04, 64-bit.  But I think I've figured it out.  My bash command history 
for that window says:

hg clone http://landley.net/code/firmware
cd firmware
ls
hg rollback
hg log -v | less

Repository was gone at that point.

I'd forgotten I did this in a fresh checkout of the repository (in an attempt 
to make that weird not-quite-there uncommitted merge commit go away).  The 
rollback didn't trim off the last commit in the repository, it apparently undid 
the _clone_.  (Which was not the behavior I expected, but I suppose makes 
sense in retrospect.)

I still don't understand what an uncommitted merge commit _means_, or why such 
a halfway state would exit.  Nor why it tries so hard to involve the current 
working store in pulling somebody else's repository.  Or why it needs a merge 
commit to fix up a one line change in an area I hadn't touched in ages.

But I think I at least understand why that repository suddenly evaporated now.

Rob
-- 
Latency is more important than throughput. It's that simple. - Linus Torvalds