state: don't have a dict like interface for cmdstate class
This patch changes the cmdstate class to stop having a dict like interface and
delete the __nonzero__ function. After this patch, the save fuction takes a dict
to store the data and read function returns a dict of the data stored.
Differential Revision: https://phab.mercurial-scm.org/D3572
Test issue2761
$ hg init
$ touch to-be-deleted
$ hg add
adding to-be-deleted
$ hg ci -m first
$ echo a > to-be-deleted
$ hg ci -m second
$ rm to-be-deleted
$ hg diff -r 0
Same issue, different code path
$ hg up -C
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ touch does-not-exist-in-1
$ hg add
adding does-not-exist-in-1
$ hg ci -m third
$ rm does-not-exist-in-1
$ hg diff -r 1