When setting "history = True" in combo-layer.conf consistently for the
components involved in an update or using "update" together with the
"--history" command line flag, a new mode for updating will be used
that does not rely on exporting/importing patches.
A config setting is used because it should be used consistently by
everyone using the same config, without having to remember to use an
additional command line parameter.
There are no real global settings, so the setting is checked
separately for each component although the setting has to be set
consistently. This restriction could be removed later.
In practice, putting "history" into the "[DEFAULT]" section is the
easiest approach for configuring it.
The actual code changes split up action_update and the
combo-layer.conf handling in preparation for this new mode, without
implementing the mode itself.
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
