Philip Martin wrote:
> Julian Foad <julianf...@btopenworld.com> writes:
>> Example 3: Swapping two directory levels
>>
>> | |
>> +--A --\ /--> +--A
>> | X |
>> +--B --/ \--> +--B
>>
>> 1. alter-dir A (children={}) ### Needed?
>>
>> 2. mv-away A/B (id=”original A/B”)
>>
>> 3. alter-dir / (children={A})
>>
>> 4. mv-away A (id=”original A”)
>>
>> 5. mv-here A (id=”original A/B”)
>>
>> 6. alter-dir A (children={B}) ### Second alter-dir on same path, if
>> (1) was needed.
>>
>> 7. mv-here A/B (id=”original A”)
>
> That's inconsistent: for A alter-dir is before mv-away while for A/B
> alter-dir is after mv-away.
In what I wrote here, alter-dir(/) is before mv-away(A), and there are two
calls to alter-dir(A), in steps 1 and 6, before and after mv-away(A/B). But
anyway, yes, it's messed up, and your suggestion below is neater.
> A more consistent set of steps would be:
>
> 1. alter-dir A/B (children={A})
>
> 2. alter-dir A (children={})
>
> 3. mv-away A/B (id="original A/B")
>
> 4. mv-away A (id="original A")
>
> 5. mv-here A (id="original A/B")
>
> 6. mv-here A/B (id="original A")
Yes, that's nicer. Yes, you can probably drop the alter-dir(/) like you have
done, on the basis that the list of child names in (/) does not change even
though their identities do change. That's an under-specified part of the rules.
> Not sure whether 1 and 2 have any particular order. In the working copy
> receiver the alter-dir for A/B causes A to be added as incomplete in
> A/B; it becomes complete at step 6. I'm not sure whether the alter-dir
> for A that deletes a child causes anything to be marked.
>
>> There are two potential problems here:
>>
>> * We make an edit within subtree A (the “move-away A/B”) before moving A
>>
>> * The “alter-dir A” is performed twice
>
> In this case there is no need to perform alter-dir on A twice.
Right, good.
> As you pointed out when a copy replaces a mv-away it is still necessary
> to alter-dir two different nodes at the same path:
>
> 1. alter-dir A (children={...})
> 2. mv-away A (id=...)
> 3. copy A (src=...)
> 4. alter-dir A (children={...})
Well, that depends. There may be no need to issue the alter-dir on the
original 'A' at this stage, we could wait until it arrives at its final path
(move-here B (id="original A"), then alter-dir B).
- Julian
