[PATCH 2 of 4 V2] histedit: switch state to store node instead of ctx

[Durham Goode]

On 2/3/15 3:17 AM, Pierre-Yves David wrote:
>
>
> On 02/03/2015 12:32 AM, Mateusz Kwapich wrote:
>> # HG changeset patch
>> # User Mateusz Kwapich <mitrandir at fb.com>
>> # Date 1422314748 28800
>> #      Mon Jan 26 15:25:48 2015 -0800
>> # Node ID 5868827d6d1a2a75d9628d502281d0d7fad2b115
>> # Parent  0c8cf9835334d76f52e7cebf9d70b5b0df646871
>> histedit: switch state to store node instead of ctx
>
> (I commented on V1 before seing V2, copy pasting comment)
>
> why is it necessary to change it on the state object itself? It is not 
> obvious to me how it helps.
>
> (If you want to clean stuff in this area, feel free to also nuke the 
> last on disk usage of pickle in the Mercurial codebase (beside convert 
> madness)
Currently, if the node no longer exists, the state object fails to load 
and pukes with an exception. Changing the state object to only store the 
node allows callers to handle these cases.  For instance, in 
bootstrapcontinue we can now detect that the node doesn't exist and exit 
gracefully.

The alternative is to have the state object store something like None 
when the node doesn't exist, but then outside callers won't be able to 
access the old node for recovery (unless we store both the node and the 
ctx, but why bother).

More importantly it allows us to detect this case when doing hg histedit 
--abort.  Currently this situation results in both --continue and 
--abort being broken and the user has to rm .hg/histedit-state to unfuck 
their repo.