graft: start using the cmdstate class to read and write data to graftstate
This patch replaces the logic to read and write data to graftstate file to use
the state.cmdstate() class.
The previous graftstate format didn't had any version number on top of that, so
we have to catch the CorruptedState error and then read the graftstate in case
of old state files.
This will help us to implement nice additions to graft commands like
`--no-commit`, `--abort`, `--stop` flags.
Passing on test-graft.t shows that things are working fine.
Differential Revision: https://phab.mercurial-scm.org/D3654
#require docutils gettext
Error: the current ro localization has some rst defects exposed by
moving pager to core. These two warnings about references are expected
until the localization is corrected.
$ $TESTDIR/check-gendoc ro
checking for parse errors
gendoc.txt:58: (WARNING/2) Inline interpreted text or phrase reference start-string without end-string.
gendoc.txt:58: (WARNING/2) Inline interpreted text or phrase reference start-string without end-string.