[darcs-users] darcs patch: resolve issue864: check non-force replace against pending (and 2 more)

[Tommy Pettersson]

Hi,

On Thu, Oct 16, 2008 at 07:09:52PM +0100, Eric Kow wrote:
> Hi Tommy,
> 
> On Sun, Oct 05, 2008 at 15:44:47 +0200, Tommy Pettersson wrote:
> > Here is a fix for issue864 -- sort of.
> 
> Do you still want these patches to be reviewed / go in?
> 
> Thanks!

> > Sun Oct  5 01:57:19 CEST 2008  Tommy Pettersson <ptp at lysator.liu.se>
> >   * resolve issue864: check non-force replace against pending
> >   The replace was checked against pure pristine, so the answer to if it could
> >   be applied to pending without force was sometimes wrong.

I started looking deeper into this, but never finished. (I think
the dialog for reverting changes can be improved.) Anyway, if my
understanding that new pending changes are added at the end of
previous pending changes, then I think the above patch is
correct and should be applied. If my understanding is wrong the
patch may be incorrect, but the intended change is still how to
fix issue864.

> > Sun Oct  5 02:03:16 CEST 2008  Tommy Pettersson <ptp at lysator.liu.se>
> >   * make replace safe (again)
> >   If the new token exists in either pending or working, the force flag must
> >   be used, because otherwise some unrecorded changes may be destroyed when
> >   those tokens are modified to allow the replace.
> > 
> > Sun Oct  5 02:52:23 CEST 2008  Tommy Pettersson <ptp at lysator.liu.se>
> >   * rewrite issue864 test to check for the real cause of the bug

These patches will change darcs Replace in a noticeable way, and
are probably not what the original poster of issue864 intended.
Why and how is hopefully crystallized in the last paragraph of
this email.

Current darcs requires --force only if the replace is unclean in
*both* recorded and unrecorded. I fail to see the logic in this.

If the replace is clean in recorded but unclean in unrecorded,
then unrecorded is modified in a way that can't be exactly
reverted. This is fine, since editing a file can also change
unrecorded in a way that is not exactly revertable. If the
replace is clean in unrecorded but unclean in recorded, then
darcs will insert hunks in pending. This is also fine, since
these hunks will not necessarily clash with unrecorded changes,
so an exact revert is often possible, and when it isn't, the
situation is no worse than for the above case. But then I wonder
what's special with an unclean replace in *both* recorded and
unrecorded. Why does it require the --force flag while the other
two cases don't? The possible revertability will be no worse in
this case.

My thinking is the --force flag should be required in all three
cases, or in none of them, and personally I prefer all of them.

Regards,


-- 
Tommy Pettersson <ptp at lysator.liu.se>