We now invoke curtin install in a step-by-step mode. Before, we would
perform a single invocation of curtin install for the following stages:
* early (but no early_commands configured)
* partitioning
* extract
* curthooks
* hook
* late (but no late_commands configured)
We now run multiple invocations of curtin install, in 5 different steps:
* initial: does not run any stage per se but prepares curtin
for the next invocations (this invocation is not strictly necessary
and could be merged with the next step but having it separate makes
the flow easier to understand, I think)
* partitioning: runs the partitioning stage
* extract: runs the extract stage
* curthooks: runs the curthooks stage
The early and late stages were dropped since they would act as no-ops.
We also dropped the hook stage since it does nothing in Ubuntu.
The configuration files for each step ends up in
/var/log/installer/curtin-install/subiquity-{step_name}.conf
The log files for each step end up in
/var/log/installer/curtin-install/{step_name}.log
If errors occur, a tarball of the necessary logs end up in
/var/log/installer/curtin-install/{step_name}-error.tar
All files (i.e. configuration files, log files, error-files) are bundled
in the apport report in case of crash.
Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>